pCP 6: can't turn Jivelite *on* with Slim remote power button

I have IR working pretty well with Jivelite/pCP with the official 7" screen 6 using keytables/GPIO/TSOP4838, but I have encountered one weird thing -- while I can use a genuine Logitech Squeezebox remote to turn Jivelite off with a single press of the Power button, I cannot turn it on that way. If I tap the power button on the SB candy bar remote when Jivelite is off, I see a flash of an "on" screen but a fraction of a second later it turns off again. I am able to go from off to on by tapping the left arrow on the remote, but not the power button. This even happens when connecting to a "clean" instance of LMS that runs no 3rd-party plugins. I am using the Custom Clock applet but this behavior happens whether I'm using that for any screensavers or not.

Any ideas?

pCP / LMS info:
piCorePlayer v6.0.0 | www v0005 | linux 4.19.105-pcpCore_v7 | piCore v10.3pCP | Squeezelite v1.9.6-1206-pCP | LMS 7.9.2 - 1578996832