Hi
Searching by that message leads to rather old issues on the ixgbe drivers. X520-DA2 are pretty old by now (but still very useful) so most issues should be ironed out by now. If used them in a couple of systems (not PVE though) and they are among the most stable cards, (when comparing the early and sometimes still weird issues I've encountered with X710 cards running old NVM firmware.
In contrast to more recent Intel NICs, the X520 had much less firmware code, but i.e. HPE did release a couple of firmware updates it is branded version of these cards (HPE i.e. 560FL and 560FLR) this might be worth a try. The cards have been branded by several server nanufacturers so you might have to identify the original vendor and then look for the firmware for that specific card.
If no firmware update is available, one person suggested in a bugreport, is to disable 'lro' as found here: