I’m having this exact issue. Maybe we can support one another. Have you gotten any further?
For anyone who stumbles across this thread with Pandora issues: I could NOT fix this issue in Picroft so I moved to Mycroft installed on a Raspberry Pi 4B and it worked smoothly. The issue appears to be several compounding problems in Picroft. When adding the Pandora skill on Picroft I consistently received dependency errors which I corrected manually through apt but once everything was installed the playback speed error persisted. This issue remained across reimages of the SD. Mycroft running on the Pi 4B doesn’t have any dependency issues when installing the Pandora skill and also didn’t have any playback speed issues.