End ferrules not fitting into Shelly relay screw terminals?

I’m adding some of the newer Shelly relays (e.g. Shelly 1PM Mini Gen 3, or the Shelly 1PM Gen 2), and I’m having a lot of trouble getting end-ferrules to actually fit in the screw terminals.

Fro example, using 2.5mm wire - the bare stranded wire will fit in the screw terminals. However, the same wire in the appropriate end-ferrule won’t fit in the terminal.

I’m using the Knipex Twistor16 crimper, with the blue DIN26228 sleeves.

(Somebody else mentioned a similar issue on the Shelly FB group here - but there wasn’t really an answer).

Does anybody know of anything that might work here?

Is there a different crimper, or crimping sleeve that could work?

Perhaps these insulated crimp lug pins: