Custom page no longer working?

Hi. Thanks for this plugin – lightweight, customisable, access token etc., just what I was looking for.

However since the recent update I’m not able to use a custom page. I use this plugin on multiple websites and they all now only display the bare content of a custom page – the main elements are no longer included – doc head, CSS, scripts etc. On one or two sites the custom page is displayed empty, requiring the default message to be used instead – this has been the case on those sites for a while now, since before the recent update.

I use GeneratePress (incl Premium) and GenerateBlocks Pro for all my sites, and everything is up to date plugin- and theme-wise on all. Is there anything about GP which would prevent the custom pages from displaying properly? They were nearly all working fine until recently.

I’ve not shared any links as in most cases the plugin is used on staging/development sites which are obv not yet public, but I can share a link or two privately if nec.

TIA.