@e selector cannot find players anymore it seems.
/say @e[distance=..5]
does not make me say my name, but
/say @a[distance=..5]
does.
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This happens even after stopping and starting the server again though, seems to happen all the time, rather than after teleporting.
Running the first command worked as expected for me. This sounds like MC-92916.

Neko, I just said I even restarted the server a few times, while relogging alone corrects the entity lists already, and I never teleported. This is not a duplicate of that report.
Are you able to reproduce this in singleplayer?

Iād have to check that tomorrow.

After further testing, it seems you were right, there must be some command block in that world that teleports me to myself the moment I log in or something alike.
Interestingly, this didn't happen in 50a.
I had the same thing happen in 18w50a after teleporting around a bit. Wasn't able to find a good way to reproduce it though.
It seems that under certain conditions entity end up not being updated correctly on all lists.
When entering [distance=..n] in an entity selector, it will likely use the chunk-wise entity list.
Player selectors may prefer the global player list in most cases though.
So if the player entity is missing on the chunk-wise list it won't be found by the entity selector, but would still be found by the player selector.
Maybe try @e[type=player] without a distance and see if that is able to find the player. That would further confirm that it is caused by the lookup on the local list.
Oh yeah and MC-141484 might be related.