The errors are just clocking up.
I often see many more errors than that over a similar time period.
What is unusual is that you seem to be achieving more from the 2nd band plan than the first band plan.
Asbokid has already suggested possible reasons.
Ongoing graphs of your connection over an extended period via the START_LOGGING_24-7.BAT script may be able to identify definite patterns regarding times and/or types of issues such as SNRM drops that might be able to be linked to events like REIN from a nearby neighbour's house etc.
The unusual spike in your Hlog graph may not have much (if any) impact as it occurs at the higher frequency band plan that isn't available for your connection when it re-syncs, unless it is that that actually stops you achieving anything.
I doubt it though as a spike in the Hlog graph actually means lower attenuation at those tones/frequencies.