You can try as hard as you like but item frames are now the bedrock of creative mode. Please fix soon.
-Soul
MC-157562
Item frame
Resolved
Cannot Reproduce
0
I tried to recreate your said issue but had no luck with a vanilla server running 1.14.4 and 1.14.3.
Unfortunately it seems the issue is isolated to you. It could be possible you are using a modified server file? like spigot or bukkit?
If that is the case there isn't anything that can be done from Mojangs side. I would recommend updating the server and testing again. I tried to recreate the issue with OP and without OP and between Creative and Survival Mode with no luck it is working 100% as intended. check the console of the server if it happens again to see if there is any errors on that side if there is post a screenshot so it can be investigated.