No Pinch or Smart Zoom

At work I have a Magic Keyboard & Trackpad (rev 1, with the AA batteries) connected to my 2014 MacBook Pro.

About 80% of the time everything works as expected. But occasionally I find that the trackpad smart zoom and 2 finger pinch zoom don’t work. I’ll put it to sleep to take home or to a meeting and inexplicably it works again the next time I’m back at my desk.

When it fails I try toggling bluetooth off and on, and both zoom functions in system preferences, but noting impact. And of course, I’m looking for a fix which doesn’t require a restart or any interruption.

Can anybody suggest anything?

When this happens does it just affect the Magic Trackpad, or smart zoom and pinch to zoom also fail on the MacBook Pro’s built in trackpad?

My recollection is yes, they also disappear from the MacBook’s trackpad

Back in the office this morning, and all is well… for the moment.