Thanks @porthos
In preference to my following spiel, it seems like it is now working (although there was no obvious sign of downloading an update). Thanks for your quick reply.
What I did was the following:
I enabled the "allow beta updates". However, when I check for updates, I am still informed that I am up to date. I tried restarting malwarebytes and even rebooting, but I'm still "up to date".
Do I need to allow some time to go by to allow the updater to find this update? Alternatively, can I tell it apply a specific update (i.e. the one you refer to)?
FWIW, my version info appears to be later than the version info you provided above.