rhel7: The system clock gains greatly after starting ptp4l and phc2sys

Issue

In the customer environment, the system clock gains about 40 years after starting ptp4l and phc2sys.

• 1) The PHC showed the correct time, as verified with phc_ctl:

  # phc_ctl eth20 set; date
  [..] phc_ctl[595205.444]: set clock time to 1547722045.199808833 or Thu Jan 12 11:43:25 2019
  [..] Thu Jan 12 11:43:25 CET 2019
  

• 2) The system showed correct time, verified with the 'date' command.

• 3) These were run:

  # systemctl start ptp4l.service
  # systemctl start phc2sys.service
  

• 4) The system time jumps by 40 years, ad these messages appear:

  ptp4l[1208]: [123169.261] master offset 62234514012 s1 freq   -6805 path delay      47   29
    :
  ptp4l[1208]: [123219.252] master offset 1547722045.199808833 s0 freq   -6805 path delay         2704
  

There is no time difference from the master clock. The correct time is set in PHC. Has Red Hat detected cases that the system clock gains greatly in an environment using PTP? A 3rd party driver for i40e is in use.