Jonny

Hey Edward, I think you triggered this bug;

https://bugs.mojang.com/browse/MC-134105

I was just thinking about and popping back to add that, so thank-you Quadrato.

Regarding that, the first time, I copied the DIM1 folder from a week old backup, before I had even found an End Portal. I'm still not entirely sure what happened as it recovered me from the bug, yet didn't delete The End and after closing the game, had 4 different dated region files (- 0.0 , 0.-1, -1.0, -1.-1) from the corrupted version of that folder. All dates were from after the bug first occured, the discrepencies were a few hours younger on those four files in the 'repaired' version.

Sorry, I know that isn't a great explanation, I've been rather confused by the whole thing lol

Tails1 (Minecraft Forum) just helped by referencing this bug thread, great to see you've already got it resolved.

I wasn't sure whether to post a comment or not, though if anyone is stuck between now and the release of 1.13.1, I did find that deleting the contents of the DIM1 folder resolved the issue, as a temporary workaround. This does only work until you go back through the exit portal of The End again.

Built a slime farm yesterday not knowing there was issue with slimes spawning. I also found a few slimes while making it but now they never spawn just like Joseph said. I've been looking all over the internet for solutions and made some creative worlds to test slime spawning within slime chunks. What I found is the only way I can get slimes to spawn is to expose them to sky light like (https://bugs.mojang.com/browse/MCPE-30413). This means you would have to dig out all the blocks above a slime chunk just for slimes to spawn on one floor of a farm. This should really be fixed.