Marcel
The issues is associated with this change.
DST Root CA X3 Expiration (September 2021) - Let's Encrypt
His device is android 7. Sometimes the TLS works but not perfectly. I'm sure their are others on older devices that have issues since CA expired. As seen above older systems and devices don't have updated root CAs.
I need to look into another TLS cert issuer that has root CA on older devices. A internet issue of devices lasting longer and thus creating compatibility issues. This problem will only grow with time.