Keywording breakdown

I have a very large catalog that I work from (71k files) and though I have a relatively fast system with lots of storage, some LR procedures are rather slow. Now though, my keywording has been giving me problems with addiing a new keyword. I have been trying to create a Calendar 2026 keyword ( I already have previous year Calendar keywords) , but when I try to create this new keyword, it will arbitrarily place it under another keyword (Wildlife, Birds various and so forth). While attempting various work arounds, LR seemingly erased ALL of my keywording - hundreds of them. I did not, in any way that I could see, trigger that action. It would be an immense loss to me if it cannot be easily corrected. I do have external hard drive backups, but because my files are spread around various disks in a way that I only vaguely understand ( my son has been my computer builder), I am not certain that I could put the whole agglomeration back together from the external disk. I am putting off the nightly  shutting down the computer for fear of locking in the erasure. Has anyone out there had anything like this happen and might offer suggestions? Thanks for reading.   Tom