I discovered, as a result of not getting any reasonably lengthy piece of content synchronised back to the server, that there was a message in the apache log alluding to me trying to send a POST message of more than 1024 characters.
It turns out that this is controlled by a variable in the apache conf file, so as a result of the recent wxjs upgrade, the wxjs stuff in the conf file now needs to look like
LoadModule wxjs_module "d:/wxjs/bin/mod_wxjs.dll"
AddHandler wxjs .wxjs
I.e. APREQ2_ReadLimit has to be set to be some reasonably sane value large enough to represent your largest expected POST message size (i.e. when synchronising content to the server).
If not, you’ll get an OK response from the call, but the content won’t be synchronised, and you’ll only know for sure that there’s a problem by seeing the message in the log file.