I read this and looked your prison and (unless you've fixed them yet) i found few problems here..
As you can notice (from that border in the first picture where that toilet is facing downwards) that the long shower area close to the road you have is not marked for it's entire length and the showers on the left side of the prison is not marked at all, which is why all the prisoners wants to use that part on bottom right.
After extending the shower room close the road and adding shower room on left side:
Second problem (or problems) you have is.
With eating times (problem is not with the regime) but rather with those two canteens.. In that save file you uploaded, atm you got 312 prisoners out of 595 and on each canteen you have _only_ two serving tables per canteen, which is FAR TOO few when you should have between 10-20 in each canteen (as each serving table can hold 40 meals (a guess, not completely sure)).
Second problem that those canteens have is tables and benches.. each of those bench-table-bench sets have seats for 8 prisoners to eat and you got 17 sets in each canteen, which totals 272 seats for prisoners to eat and you got 312.
Another thing which might be a problem is the amount of fridges and cookers.. you got 7 fridges and 7 cookers when prison of that size safer bet would be double the amount you have now.
And also you got moderately big kitchen but only 20 cooks, which is causing the problem that those cooks can't do all that work in time before next meal time is already coming up, so better amount would be i.e 40 cooks. (if you look all those dirty foodtrays stacked in the sinks waiting to be washed):
Third thing what is a possible problem is to do with the phones and tv's you got (or the lack of) in your prison.. I counted total of 34 phones and 46 tv sets scattered around the prison, where the tv's on lower part of the prison is facing the wall (not sure if that is the problem).
But the problem with phones and tv's is, that there is way too few of each for those 312 out of 595 prisoners to be used when there is Free Time periods in the Regime or during Work hours if all the prisoners don't have jobs assigned to them.
This can be seen with that red "Critical" indicator in the Needs section with "Family" and "Recreation" bars.
Also as can be seen on those fixed shower screenshots, by the time i played the save till end of the current Meal time in the Regime and changed the following 2 Work hours into Shower time, the Threat level indicator reached full. (in real time, about 5 minutes)
