This has been happening to me since 1.16 and I see MCCE-3270 from years ago about the same topic but was never resolved.  Everyone on our servers are affected by this.  It happened right after the 1.16 release...I believe it fixed itself in 1.16.1/.2 because I was able to fish again with no issues - but now in 1.16.3 it is happening again.  Cast the lure and after about 10 - 15 seconds with random timing it simple reels back in unprompted.