No it should not be resyncing like that. Even in the 10 day period is abit overrated, the DSLM is always monitoring your connection and adjusting your target SNR and interleaving settings to provide a stable connection.
The 10 day period is to make sure this process has been given enough time to work before they investigate further.
Just one thing, the hub 4 itself doesnt contain the modem so check the lights on the white vdsl modem and see if the dsl light is also flashing at the same time. If so check the wiring to master socket. Also check your extension wiring to make sure its not a problem internally otherwise they may charge you during a visit.
Check out this guide to test without internal factors.