Damn, I've a Similar Situation Happen today. I was working on a Project, Hit the Save Button cuz I had to leave. After it Saved Exited out of LMMS then Hit the Physical Power Button on my Computer. Came back tried to load up the previous file I saved. It said " The File <File Name> seems to con...
I Already Solved This Exact Problem.
Use the VST Tuner and it will tell you what root note your 808 plays. Tunes 808s PERFECTLY EVERYTIME!
https://lmms.io/forum/viewtopic.php?t=30168