I've painfully look through all 71 of them. And I didn't find anything wrong at a glance. And I look several what you said with both lv9 and lv8 factory. I see they either
1) Don't have training budget, so as expected won't level up obviously, like factory 40
- William_factory40_before.jpg (204.84 KiB) Viewed 1381 times
2) On its way up from level 8 to level 9, still under training, like factory 29
- William_factory29_before.jpg (197.65 KiB) Viewed 1381 times
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I let the game runing for about a month, and set all the factories with training budget full, and here is the result
1) Factory 40's manufacturing unit start to level up, as expected when it has training budget.
- William_factory40_after.jpg (203.18 KiB) Viewed 1381 times
2) Factory 29's manufacturing unit continue to level up, notice the number of blue uniform workers is now 4, instead of 3.
- William_factory29_after.jpg (194.01 KiB) Viewed 1381 times
By my estimation, since about 1 or 1.5 worker is trained from red to blue. So in factory 29, the remaining 20 workers would take a year or a year and half to be trained and this unit will reach level 9.
I don't see obvious issues here. I think the problem is only because the left side unit has priority over right side unit, hence it leveled up faster. And since you are constantly researching technology, once applied, the level 9 unit drop to level 8 (or lower again), and on their way training back up, the technology update again, thus making right side unit a little behind left side unit from time to time.