It sounds like the BP got corrupted. This unfortunately happens once in a blue moon, and there is yet to be a solid explanation from anyone as to why and how.
The player BP in our game is pretty massive and only gets bigger, so there doesn’t seem to be any kind of limit. You should be fine to continue working in it.
Today I was programming in blueprints as always, and at one point whole my sistem started to freeze, task manager shoved 100% load on Hdd. I had 3d’s max scene opened at this time, so I thought may be it’s to mach for my laptop, so i closed 3d’s max, and started to wait Unreal engine to unfreeze. 5 minutes later I decided to stop the Unreal engine task, because it did not respond. Then I restarted my laptop, and project. I tried to open the blueprint I was working on and engine froze again - restart, try to open blueprint file and frose again. I thought I lost my project, but later I found an autosaved backup file from yesterday, so I lost only todays work.
So the questions are - did I hit the blueprint size limitation (file was 3.5 Mb)? or did the blueprint broke when I closed the engine with task manager? Should I continue adding functions in this blueprint, or wait for 4.8 and hope epic add exposed variables for add child component function?
I found the problem - somewhy for loop with break cannot be restarted with second input node, it freazes the engine on compile and will not allow to reopen the blueprint.