[SW] 18412 kHz CW - UNID - getting stuck at numbers but sending some letters at times, Jun 28 2024

Another mystery signal from the shortwave bands, and it's a Morse one!
On late morning of June 28th, 2024, somebody was running a strange, continuous transmission on 18412 kHz, sending out a single digit over & over for a few minutes, followed by a set of a couple letters, only to get into another digit & get stuck with it for another few minutes. This pattern continued for quite a long time, mostly getting stuck at single digits, and sending meaningless, ungrouped strings of letters in-between.
Besides, if you listen to the signal more closely, you can note it skips up in frequency a little, as briefly as an eye blink.
The unknown nature, and the above defect, had prompted me to try an audio waterfall, as I was setting up SDR-Console following a hard-drive replacement in my laptop. On some fades, you can still copy a symbol graphically, even if you have a hard time hearing it!
Any questions about this signal can be directed anywhere but me, since I know nothing about it!
This extended sample was caught at 09:35-09:50 UTC June 28th, 2024 on 18412 kHz CW, in NE Poland, using Airspy HF+ Discovery & ~12x4.5m vertically mounted loop antenna.