black screen when send_to_screen_1 after send_to_screen_2

When player a video an pressing ctrl+2 (send_to_screen_2) a fullscreen mpv-window opens, playing the video on the 2nd screen. If I press now ctrl+1 (send_to_screen_1), the mpv-windows closes and the smplayer-window show a black video-screen and the audio of the video is playing.
Pressing ctrl-2 again shows the video on screen 2.

dpkg -l smplayer mpv
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-===============-============-======================================
ii mpv 0.34.1-1ubuntu5 amd64 video player based on MPlayer/mplayer2
ii smplayer 22.2.0~ds0-1 amd64 Complete front-end for MPlayer and mpv