What language you selected in the drop box? Try with both Undetermined and English.

It might depend what instance you signed up through/device you use. I was having troubles from desktop with lemmy.world, but they did some tech voodoo magic for the server it's hosted on so it's been mostly smooth all week. It's consistently worked pretty well from the jerboa app for me tho

Seems to occur in older browsers for some reason, although Lemmy in general can be laggy with posting.

By any chance, are you using an older browser?