In the character editor: 

- Trying to load a character into the editor when there is nothing to load, will crash the game.

Log:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_ListPopup:
Variable Index [0] out of range [0] - 31.102361(102361,0)------------------------------------------
STACKTRACE:
>> gml_Script_anon@5779@anon@5661@charEditor_LoadCharData@_CharEditor (line 157)
>> gml_Object_par_ListPopup_Alarm_0 (line 3)

- Invalid inputs (text instead of numbers or incomplete info, like missing a comma) in most input dialogues will crash the game.

This happens on:
Char > Set Ver., and Set Palette.

Sprite > Import Sprite (When it asks you how many frames of animation), Set Speed, Set bbox, and Set Origin.

Log(s):

For Set Ver:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
unable to convert string ":3" to number------------------------------------------
STACKTRACE:
>> gml_Script_anon@14782@charEditor_EditCharVersion@_CharEditor (line 315)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

For Set Palette:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
unable to convert string "" to number------------------------------------------
STACKTRACE:
>> gml_Script_hex (line 7)
>> gml_Script_anon@15028@charEditor_EditCharPalette@_CharEditor (line 324)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

For Import Sprite:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
unable to convert string "a" to number------------------------------------------
STACKTRACE:
>> gml_Script_anon@16364@charEditor_ImportSprite@_CharEditor (line 355)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

For Set Speed:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
unable to convert string ":3" to number------------------------------------------
STACKTRACE:
>> gml_Script_anon@17759@charEditor_SetSpriteSpeed@_CharEditor (line 386)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

For Set bbox:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
index out of bounds request 2 maximum size is 2------------------------------------------
STACKTRACE:
>> gml_Script_anon@18905@charEditor_SetBBoxMenu@_CharEditor (line 417)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

For Set Origin:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
unable to convert string "" to number------------------------------------------
STACKTRACE:
>> gml_Script_charEditor_SetSpriteProperties (line 431)
>> gml_Script_anon@18318@charEditor_SetOriginMenu@_CharEditor (line 403)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

For the Level editor:

- Invalid inputs in some dialog boxes will also crash the game.

Affects:

Level > Set ver.

Edit > Resize room

Log(s):

For Set ver.

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
unable to convert string "a" to number------------------------------------------
STACKTRACE:
>> gml_Script_anon@24182@editor_EditRoomVersion@_RoomEditor (line 619)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

For Resize Room:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_Dialog:
unable to convert string "a" to number------------------------------------------
STACKTRACE:
>> gml_Script_anon@10600@editor_ResizeRoom@_RoomEditor (line 289)
>> gml_Object_par_Dialog_Alarm_0 (line 8)

- Clearing BGs after they're been cleared will also crash the game. 

Log:

EXCEPTION:
ERROR in action number 1
of  Step Event0 for object par_Toolbar:
sprite_delete argument 1 invalid reference to (sprite) - requested 751 max is 853------------------------------------------
STACKTRACE:
>> gml_Script_editor_ClearBGs (line 800)
>> gml_Object_par_Toolbar_Step_0 (line 46)

Invalid PNG images will crash the game when you try to add them as xtra decor or BG objects (same thing happens on the character editor)

Log:

EXCEPTION:
ERROR in action number 1
of Alarm Event for alarm 0 for object par_ListPopup:
sprite_set_speed argument 1 invalid reference to (sprite) - requested -1 max is 853------------------------------------------
STACKTRACE:
>> gml_Script_anon@19909@editor_AddBG@_RoomEditor (line 564)
>> gml_Object_par_ListPopup_Alarm_0 (line 3)

I found this one by accident, as I tried to add a PNG that turned out to be a WEBP disguised as a PNG.

I am not fond of WEBP...

--

A strange crash related to Multiplayer:

- Joining a server, quitting (or failing to connect), then attempting to host, will crash the game if you exit the server once it's been hosted.

Log:

EXCEPTION:
ERROR in action number 1
of  Step Event0 for object obj_HostScreen:
Unable to find any instance for object index '233' name 'obj_shell'------------------------------------------
STACKTRACE:
>> gml_Object_obj_HostScreen_Step_0 (line 44)

As for miscellaneous things that don't crash the game but could potentially cause issues:

- You can load multiple saves at once if you're fast enough, which sometimes makes them bleed data (Trinkets and level records, sometimes  player names) into each other.

For example, your online save being auto-loaded still gives you time to go and load an offline save (or multiple of them!) Ultimately the online data will be loaded first, but with mixed data from the other saves. 

- In the level editor, after clearing BGs, exiting the editor and playing normally will give some levels a milky white sky, which looks neat.

- You can pause the game while testing your character in the char editor. Which causes some odd behaviour, like being able to play (with all of your acquired weapons) while you edit a character (since you can restart the level).

thank you for the reports! most of these bugs should now be fixed in version 1.1.2.1.

the only one i couldn't fix was the background clearing issue. it already has conditions which should check if the background sprite isn't the one set in the room editor's background layers, but it doesn't seem to work. i will need to investigate it sometime later though.