403 error when updating form

I have three sites that I use Forminator on, all of which I have updated to WP 6.7, and all of them using the latest Forminator. I have tried to update various things on forms, but on clicking Update I get “Something went wrong while saving your form. Please try again.”, but only on two of the sites. They all use the same theme, Blocksy (and the Blocksy Companion plugin), but the one that is OK does not use any other plugins that the others use. The console/network logs report 403 errors pointing to the forminator/build/form-scripts.js file (unreachable code after return statement form-scripts.js:66:117709) but I think this may just be where the error message is, rather than the source of the problem. However the full log is below for reference:

Error: Request failed with status code 403

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:46

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????onreadystatechange https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:46
form-scripts.js:123:324986

Error: Request failed with status code 403

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:46

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????onreadystatechange https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:46

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:46

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:46

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????promise callback*i.prototype.request https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????r https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????exports https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:46

????value https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????value https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????setTimeout handler*value https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????value https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:123

????mt https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????mt https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????Gr https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????Gr https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????Kr https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????tn https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????Is https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????ot https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????tn https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????ba https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66

????ha https://mysite.com/wp-content/plugins/forminator/build/form-scripts.js?ver=1.36.3:66
form-scripts.js:123:324986
?

So now I turned to the plugins that are common on the two not working sites, and even with deactivation the problem is still there.

I have contacted my host as I suspect the issue lies there, and he has already made one change to the web filters (as suggested in another post), but the problem has not been fixed. I wanted to post here in case there was any suggestions or others with a similar issue – I have looked at other posts and tried the solutions that worked for them but nothing has so far had any affect. I have been clearing the caches (site and browser), turned off any optimisation and cache plugins, had a direct comparison of sites that had and hadn’t updated to the latest WP, and to ones that hadn’t updated to the latest Forminator. In my efforts to find the problem I also discovered that several of my sites I can’t save page edits (and I suspect even create new pages) because of a 403 error, which is why I think it is likely to be a hosting issue, although confusingly this is not consistent across all the sites I have with this host. As Forminator has not been updated since WP 6.7 came out, is it possible that it needs to be and might partially solve my issues?