Hi Vincent,
I opened a support request and got the answer as shown below.
It seems to be a long standing issue but still without result. I believe this way we keep running in circles.
@superdiver – I believe you submitted a Bug Report (https://www.nextgen-gallery.com/report-bug/) and I responded there if that is the case; but, if not, I can say we will be looking into this but do not currently have a time-line on when our developers will be able to review the issues with the Custom Area plugin.
I would suggest reminding “Vincent Mimoun-Prat” to review this and other issues with his plugin as well, as there have been recent updates to his plugin and he may be working on a solution as well.