On Factorio 1.0, it seems like the mining speed is not the number of items mined since the last update, but an average over a longer period of time. I do not recall this being a problem in Factorio 0.17 and earlier. This is especially noticeable on ore fields with a highly variable production (a high production, but only occasional trains fetching ore) or as an ore field is drying up.

The first case will show production long after all belts are fully backed up, and the second case will show that production is higher than it actually is, with the production rate very slowly dropping according to YARM, even though the extraction rate is constant.

I am also experiencing this.

Fix for this issue:

File: resmon.lua
Line: 641
Fix: Change "if delta_ore_since_last_update > 0 then " to "if delta_ore_since_last_update ~= 0 then"

"delta_ore_since_last_update" is always 0 or a negative number, thus this condition is never true.

Thank you for the investigation! I'm not currently actively maintaining YARM, but I'll try to remember this for the next release.

Just a reminder that this bug still exists. If you could fix it for the next release that would be great.

I was wondering why YARM was off by a factor of 5+ sometimes. Seems this is why.

Just noticed the same issue, especially noticeable with cargo ships and offshore oil.
Fix from FrantzX still works.

Yesterdays's release should've improved this.