I am having two issues (so far) with 9.4.0 4190-29 on my 4630X Premiere+, which is connected to my Sony STR-DH590 AVR and then to my LG OLEDB7:
1) I am no longer able to cast from my Windows 10 laptop. The Premiere shows up as a device on the Windows Connect. The cast starts but the Roku just hangs at the "pearing" screen and eventually the attempt times out. This worked fine on the pre-9.4 firmware and I can cast to the LG OLED w/ no issues.
2) To play music via RMP, I turn on the TV to start the RMP and find the DLNA server. I select the music I want to play and things start out fine. However, as soon as I power off the TV the music stops and RMP quits. Playing music from the SiriusXM or Pandora apps is unaffected when the TV is turned off, so I believe this must be a 9.4.0 problem rather than something w/ RMP.
Update: I tried my old Roku 3 with 9.3.0 replacing the Premiere+ and had no issues with casting or the RMP 5.4.4 dying when the TV was turned off. Oddly, when I put the Premier+ back on the same connections, casting started to work but RMP continues to stop when the TV is turned off.