I have no idea. I have never worked with wordpress.com hosting.
The reason I asked about other ACF addons is that I have run into some in the past that cause a premature initialization of ACF that in some cases could cause the issue that your are seeing. The order of plugin initialization can change based on plugin activation order and this includes when they are updated. So, if there is a plugin that is causing premature initialization this could change and seem random based on the last plugin that was updated/activated.
Premature plugin initialization could also happen in the theme.
Basically, premature ACF initialization can happen whenever an ACF function is called before the acf/init action. This action happens on the WP init action at priority 10. The order that init actions happen at a specific priority is based on when they are added, which is also a function of the order that the plugins are loaded which is a result of activation order. This does not happen with all ACF function calls. Basically if a function is called before ACF has been initialized and that function requires ACF to be initializes then ACF will try to initialize then, but there are some things that will not work if this happens too early.
Most of the time when I’ve seen this happen it has been with plugins that add new ACF fields or modify existing ACF fields.
