pcp4 + jivelite + lirc can't power on squeezelite player

I have the same problem as mutant_matt described in this post
I run pCP4 on a RPi3b+ with a TSOP38438 wired directly to GPIO27, 3V3 and GND: no R, no C.
My display is a cheap 320x480 LCD I run by the piscreen overlay.

My SB remote control works flawlessly when I configure pCP without jivelite.
But as soon as I run jivelite I nearly can't switch on the squeezelite player by remote. Once on, the remote works nicely again and can also switch off the player.
But when off, a press of the power button very briefly switches on the player and in an instant the player goes off again.
irw tells me that that only a single key-press is recorded.
Sometimes I am lucky and two, three, or four presses of the power button on the remote start the player. But most often it just flashes up and goes off again.

Any idea how I can make a remote work also for jivelite?
What is the difference between the jivelite and non-jivelite configurations? I tried swapping the lircd.conf file for a test but to no avail.
What can I test?

Thanks in advance

edit: I just realised that any keypress will start the player without problems. Its only the power button that doesn't work properly. I did try values from 0 - 10 for suppress_repeat in the config file. But nothing changes.