We also have the same symptom where client is also affecting.
This is purely Meraki BUG where TAC is extremely clueless on what it is..
Even with issue state its very strange that they never bothered to deep dive and capture the real issue.
TAC informed that the issue can be due to full power in 2.4Ghz and forced us to remove the static power and change it to auto. We informed that the settings were done as per the site survey with Ekahu however, Meraki TAC engineer never listens..
Anyway I have upgraded the firmware to 26.1 Beta and the single packet flood is not listing.