Just to be clear when I made the comment:
I would have thought that the latching relays was unique to this product but from your post is sounds like they have been having problems with other models.
, I was referring to Gossen products.
As I said, the Agilent 1252b also uses one latching relay in the AC/DC path. A lot of older Philips/Fluke scopemeters also in the attenuater circuit.
My old Fluke 97 scopemeters use them. Out of interest, I used that same magnet I used to demonstrate the problem with the Gossen Ultra to see if the Fluke was sensitive to it. I tried moving the magnet all about the case and it had no effect. So I brought out the tape eraser and held it right next to the case fully expecting the relays to chatter but nothing.
Mine is using Takamisawa RAL3W-K. These are physically much larger than the relays used in the Gossen. They also have some metal shielding around them which may help.
https://www.fujitsu.com/downloads/MICRO/fcai/relays/ra.pdf