This may be caused by pinned versions or preferences not being setup correctly in your apt config, rather than a problem with the PPA. It could have been caused by the recent 117 update.

In /etc/apt/preferences.d/ you can create files to control which versions and releases are used for which packages. This is how linux mint prevents snap from getting in, (even though they package their own firefox with its own customizations). Setting up something like:

Package: snapd
Pin: release a=*
Pin-Priority: -10

and

Package: firefox
Pin: release o=Ubuntu
Pin-Priority: -10

should get it working better for any further upgrades

Using the ltConfig plugin, there is a force_proxy option