RFXCOM-Transceiver can no longer discover new devices

I have an RFXCOM 433Mhz-Transceiver connected to a Raspberry Pi 4 running Debian 10 via USB.
(Just for the record, the same setup was previously connected to a RPi 3B+ with Debian 9. I’m currently using OH 2.5M4, but I gradually updated from other milestone builds. I just note that because I don’t know when the error occured for the first time.)

I use the connector to connect to some Lightning4-devices and an Oregon weather sensor. All is working fine. However, now I want to connect to new devices and to my surprise I no longer can detect new devices as OpenHAB claims that the bridge cannot be found (the same bridge it uses happily to control the devices given above).

The bridge correctly is shown in PaperUI, I can change the bridge’s settings in PaperUI, all seems to be fine, only no new devices…

The Java Options for the serial ports are set as documented. I don’t blacklist any driver, as I also use Homegear and an 868Mhz-CUL on another port.

I have attached openhab.log - this is what happens as soon as I try to discover new devices.
openhab.log (9.4 KB)

Any idea?

As an update: I can add things and items manually, as long as I can receive then with the RFXmanager Windows app. I just have to enter the definitions manually. Autodiscovery does not work.