With latest version (15.2.0 / mac 10.15.6) when I load a clip in source panel, the text panel pops up, even if I don't have a transcript assoociated with it. Tried trashing workspaces and starting over...didn't help.
I am in an edit workspace that I customized. I close the text panel but when I load a clip (in this case multicam) it opens the text panel as well. But doesn't happen for every clip. I did try to transcribe (I have access) one of the offending multicam clips but it didn't do it right, tried multiple times but it would get the timecode wrong and jump to the end of the sequence. I have not found a document that tells how to use this feature and how to delete transcriptions from a clip. Only thing I can think of is that PPro thinks this clip has a transcription attached and so it opens the text window to show the transcript? Is that how it's supposed to work in all workspaces?
I am in the Captions work space. (I happen to be in PR Beta 15.4 Build 8; I repeated this in PR Release 15.2; same results.) I switched to a different sequence. I changed to the Editing workspace. Only the sequence I was in is open (captions; no transcription). The Text Panel is no longer open, but the Essential Graphics Panel is. So I reset to saved layout. Now EGP is closed (and Text). I open the sequence with transcription. Neither EGP nor Text Panels open. I double click on a caption, and the Text and EGP Panels open - as expected.
I closed EGP and Text. I save as a new workspace. I switch to Captions workspace; EGP and Text open as expected (Text empty because I have not selected my caption track). Switch to Editing workspace - all okay; and then to my custom workspace. No EGP/Text until I double click a caption.
I remember as issue some time ago where there were issues with customized workspaces, but I'm not seeing that either.
You mentioned trashing workspaces before. I'd reset preferences.