This problem started a few months ago. If you work with undocked panels (crucial on dual or ultrawide monitor setups), those panels disappear after you send a sequence to media encoder.
1. Premiere 24.1.0 but has persisted across the last few versions
2. Windows 10 Pro 22H2 19045.4046
3. Have a project open with undocked panels in Edit mode. Send a clip or sequence to Export mode, which changes the workspace and closes your panels. Send the export to Media Encoder.
4. The workspace returns to Edit mode, and you would expect your undocked panels to return, but instead they remain closed. To get them back you have to either reset the workspace, or switch to a different workspace then back again.
This only happens when you send to Media Encoder. If you switch back to Edit mode without exporting, or if you export directly from Premiere, your undocked panels return as expected. Not a major bug but definitely an annoying quirk.