[Investigating] Increase of CLIFFY Server errors with different alpha/numeric codes

PC - Windows 10

Screenshot or image:

5th Oct 2021 at 1954 AEDT completed final battle in weekly Faction event (Lvl 30). I expected to get a lvl 9 chest, points & move to next lvl. Instead received error message. I only received lvl 5 chest and had to replay lvl 30. Luckily it hasn’t happened in guild wars Yet. :

How often does this happen? When did it begin happening?
Previously i have had it happen mainly on my PC and occasionally on my Samsung S20…I feel it has probably been over the past month, sorry I didn’t worry about taking screen shots earlier, I just let it ride.
Steps to make it happen again
there seems to be no consistency, I can see, as to when it occurs. Other than this it’s a great game for me, thanks one & all…