This sounds like something that would be in the back end so likely not. But if spoofing user agents fixes the problem then I'd say it's evidence enough to warrant a deeper look.
Is that easy to do?
Yes. User Agent is a http header that is part of every request you send to a server. As such, it is 100% client side and it can be whatever you want, it's just a text string.
For layman users, I'd recommend using an addon for it, e.g.
https://addons.mozilla.org/en-US/firefox/addon/user-agent-string-switcher/
This sounds like something that would be in the back end so likely not. But if spoofing user agents fixes the problem then I'd say it's evidence enough to warrant a deeper look.
Is that easy to do?
Yes. User Agent is a http header that is part of every request you send to a server. As such, it is 100% client side and it can be whatever you want, it's just a text string. For layman users, I'd recommend using an addon for it, e.g. https://addons.mozilla.org/en-US/firefox/addon/user-agent-string-switcher/
Of course, you can also change the user agent string in the browser config manually. The official Mozilla support page describes the process in detail: https://support.mozilla.org/en-US/kb/how-reset-default-user-agent-firefox
When they decide to do tricks in the backend differently between browsers, there will be ways to overcome that.