Mobile IOS application randomly cant connect to site via CF

Hello there
Since last week some our clients faced with issue to connect to our site via mobile app (IOS only). Android mobile application clients work fine.
There no any changes on site’s side were made.
No matter IOS version are using (14, 15 or 16 revision) – clients get error URLSessiontask failed with error – network connection was lost. Error code – 6.
When we switch off CF – everything works fine.
We had create skip rule for mobile application requested directory - but no luck.
Tried to all managed rules set off – same result – some clients get errors to obtain info from site.
Any help appreciated