I tried both -DCORE_DEBUG_LEVEL=3 and =4, but with no noticeable differences. Where am I supposed to look for the debug output?
In another attempt I tried OTA upload within the same subnet, directly addressing the ESP with its IP address 192.168.199.40. The same happened, the upload timed out without any reaction on the invitation. As this subnet is sparsely active, the data LED on the W5500 module may be an indication of traffic going to the device. I saw it flicker each time the “Sending invitation” line got another dot added, so I am assuming the packets were actually sent to the device.
By the way: repeated builds are adding more and more ofthese error lines:
[Error 2] Das System kann die angegebene Datei nicht finden: 'C:\\Users\\Micha\\Documents\\PlatformIO\\Projects\\RS485-Bridge\\.pio\\build\\az-delivery-devkit-v4\\libFrameworkArduinoVariant.a'
Please manually remove the file `C:\Users\Micha\Documents\PlatformIO\Projects\RS485-Bridge\.pio\build\az-delivery-devkit-v4\libFrameworkArduinoVariant.a`
[Error 3] Das System kann den angegebenen Pfad nicht finden: 'C:\\Users\\Micha\\Documents\\PlatformIO\\Projects\\RS485-Bridge\\.pio\\build\\az-delivery-devkit-v4\\longcmd-1edf16a8dfab01cd43f3613a9b992520'
Please manually remove the file `C:\Users\Micha\Documents\PlatformIO\Projects\RS485-Bridge\.pio\build\az-delivery-devkit-v4\longcmd-1edf16a8dfab01cd43f3613a9b992520`
[Error 3] Das System kann den angegebenen Pfad nicht finden: 'C:\\Users\\Micha\\Documents\\PlatformIO\\Projects\\RS485-Bridge\\.pio\\build\\az-delivery-devkit-v4\\longcmd-6c0073e71529232f49235f36b0dbaf93'
Please manually remove the file `C:\Users\Micha\Documents\PlatformIO\Projects\RS485-Bridge\.pio\build\az-delivery-devkit-v4\longcmd-6c0073e71529232f49235f36b0dbaf93`
[Error 3] Das System kann den angegebenen Pfad nicht finden: 'C:\\Users\\Micha\\Documents\\PlatformIO\\Projects\\RS485-Bridge\\.pio\\build\\az-delivery-devkit-v4\\partitions.bin'
Please manually remove the file `C:\Users\Micha\Documents\PlatformIO\Projects\RS485-Bridge\.pio\build\az-delivery-devkit-v4\partitions.bin`
[Error 3] Das System kann den angegebenen Pfad nicht finden: 'C:\\Users\\Micha\\Documents\\PlatformIO\\Projects\\RS485-Bridge\\.pio\\build\\az-delivery-devkit-v4\\src'
Please manually remove the file `C:\Users\Micha\Documents\PlatformIO\Projects\RS485-Bridge\.pio\build\az-delivery-devkit-v4\src`
[Error 2] Das System kann die angegebene Datei nicht finden: 'C:\\Users\\Micha\\Documents\\PlatformIO\\Projects\\RS485-Bridge\\.pio\\build\\az-delivery-devkit-v4'
Please manually remove the file `C:\Users\Micha\Documents\PlatformIO\Projects\RS485-Bridge\.pio\build\az-delivery-devkit-v4`
Once I removed the directories as indicated, the next build ran without these errors.
Final observation: after having run for more than a week without problems, after adding the ArduinoOTA code yesterday (and not changing anything else) I had a complete freeze today without the ESP starting itself again. I had to cycle power to get it running again. 