Calvin
I know this is an older thread, but I'm getting the same message on a newly updated J3 --> J4 website.
When I have Modules Anywhere installed, the homepage of the site has the layout all messed up. A couple of extensions lose formatting, an embedded video expands to full size, etc. The news display stacks instead of being in columns, a slider has the two images stacked.
Down on the page (with debug turned on), I get the "WebAssetManager is locked" message.
When I uninstall Modules Anywhere, the page looks the way it should, with everything in proper columns, the slider works, and the news display is in four columns.
It seems that this is only an issue with the homepage, as embedded modules on other pages seem to be fine.
When I switch to the native {loadmodule} embed, everything works properly, also.
Here's site info (hidden):
Confidential information:
(hidden)
Please let me know what you find out. Thanks!
Calvin