That's by definition a non-vanilla server.
I am aware and as pointed out I also experienced this bug on a more recent version of Minecraft on a Vanilla server. Will report if it happens again on 1.16-pre3 or later I hope it has been resolved.
This happened to me twice on a server once on 20w21a (vanilla server with fabric and carpet mod) and once on 1.16pre1 (vanilla server jar).
I am aware and as pointed out I also experienced this bug on a more recent version of Minecraft on a Vanilla server. Will report if it happens again on 1.16-pre3 or later I hope it has been resolved.