How about the long ping time if the hAP ac^2 is configured as VPN client? Same issue also happens on RB951G with stable RouterOS v6.40.8.
The problem has been reported in https://forum.mikrotik.com/viewtopic.php?f=21&t=133420&start=50#p658891, when v6.43rc5 is released.
The most update information for the long ping time issue for VPN client can be seen in the following link: