We have learned that this issue is triggered by activating older resource packs in a world's Resource Packs list or in Global Resources. Until the big is fixed, you can circumvent the problem as follows.
First, for any packs you obtained from a third-party source (i.e. not the Marketplace), see if an updated version is available. (Marketplace packs are updated by the game automatically, so this step doesn't apply to them.)
If that doesn't work, you need to identify which packs are causing the problem. First deactivate any resource packs in your Global Resources list. Next, for each world you want to fix, deactivate any resource packs in its Resource Packs list, then add them back one at a time, checking after each one to see whether the problem comes back. If it does, deactivate that pack and don't use it again until the bug is fixed.
After you've fixed the problem for each individual world, use the same process in Global Resources: Activate one pack at a time and check whether it triggers the bug again.
If you're a pack author or you're familiar with how packs are made, you might prefer to identify the problem packs by looking at their JSON code. Any resource pack that uses "format_version": 1 in its manifest.json (or pack_manifest.json) file will trigger this issue. You can either deactivate it or correct the problem by changing it to "format_version": 2. You also have to add "min_engine_version": [1, 16, 0] (with an appropriate version number) to the header section because format version 2 requires it, and if the filename is pack_manifest.json I think you have to rename it to manifest.json. Please note that teaching you how to do this is not the bug tracker's job: If you try this and run into troubles, please ask for help on the Minecraft Discord.