imported custom skins are not applied on servers

In Minecraft Bedrock Edition, imported custom skins from custom skin packs are no longer being applied when joining servers.

The imported skin appears correctly in the Dressing Room and can also be used normally in single-player worlds. However, when joining any server, the selected custom skin is not applied and Minecraft instead uses a default character/skin.

This happens with multiple imported skins and on different servers. I have using custom skin packs and imported skins through the Dressing Room system for several years, and this behavior only started recently. Please help.