In answer to request for details, here are some details from end May.
May 20, 2022:
Brussels-Frankfurt Fernbahnhof - ICE 15 no problems
Frankfurt Fernb-Passau (end destination train was Vienna) - ICE 29 - more than 1 hour delay, almost missed train because of last minute track change (was opposite track on same platform, and I interpreted correctly sudden move of lots of people).
Announcements were made in German and English, but not easy to understand.
May 27, 2022:
Got email message (May 24 or 25 - cannot check now because am traveling) that return trip of May 27 had to be modified because of train cancellation. I have a relative in Passau and we went to the railway station: Bahn computer was down and nobody knew when it would come on line again. Later in the day we managed to change my ticket. Passau-Frankfurt Fernb was replaced with Passau-Nuernberg and Nuernberg-Frankfurt. Had also to change timing of return, because Nuernberg-Frankfurt to get planned connection to Brussels was fully booked.
Nuernberg-Frankfurt train was late but less than 15 minutes and connection time was about 25 min. Other trains on time.
On a previous visit to Passau, in 2013, missed connection in Frankfurt because train Brussels-Frankfurt had technical problems. Other visit to Passau, in 2018, for important family event, train Brussels-Frankfurt was cancelled and we did not receive e-mail notification before leaving home. We had to come back home and go by car to be in time for event.
Am in Passau right now, but came by car this time!
Am going to Italy from here, and for the first time in 15 years I will take trains in Italy (Ferrara-Milano, Ferrara-Venezia and maybe Ferrara-Brindisi). It will be an interesting comparison.