One character crashes/cannot load in very often

[OldPlayer]

I'd like to inquire what to do in a case when just one character has the following problem:
1) The game crashes (during zone change or just because it wants to).
2) Character cannot load in, using /stuck repeatedly during loading screen sends him to starting zone, but it cannot load up.
3) Character can be loaded after 30-60 minutes of repeated tries, restarts, PC restarts etc.

The same character has a strange problem with quests. Quests often become invisible after zone change, ie. Tome of Knowledge questbook is empty. Quests do work and kills are counted, but I cannot find out if quest is done or not unless I go to the quest giver.

Very rarely (once per total crash max, usually it does not appear) the following message appears at Launcher start:
Data.myp:
System.Exception: You need to stop application currently using the following file: data.myp
v MYPHandler.MYPHandler.WriteFileToArchive(FileInArchive archFile, MemoryStream MS)
v MYPHandler.MYPHandler.ReplaceFile(FileInArchive archFile, FileStream newFile)
v RoRLauncher.Client.UpdateWarData()

Other characters work well, only one seems to be cursed.

Can you help me, please?

[Bacta]

Not sure if the guild bug is still an issue, I had multiple people who had to leave guild to be able to log back on there characters. I would suggest trying that or asking someone to kick you then try to log in next time it happens

[OldPlayer]

Was able to log into "cursed" character and deleted the quests there. Did the same with another character. Both are logable immediately now without any problems.

Edited later: found the possible "solutions"

1) Delete all useless quests IF you are able to log in.
2) If not, try different PC, it may work. Go to point 1.
3) If you still cannot log in, delete everything associated with your character from RoR folder.