The grabber/WSPR was running on 500kHz the better part of the last 24h. To the later afternoon, I was using the HF3, hence, the frequency offset. For the evening, I changes to the AR3030, which I adjusted to the WSPR "dial" frequency. This is, when using the SSB-filter, somewhat far off for the two beacons DI2AM and OK0EMW. Using the SSB-filter helped a big deal with my local plasma-QRM.
Now that the culprit appears to be switched off... finally... it seem time to drop the filters. As of 21:36z, the AR3030 is running with the AM-filter.