Henlo,
I was grinding out on some solo bounties and as I had 4/5 of the prisons destroyed i was trying to find the last one which i found and was marked on my map but its not there. I was reading another post on here where someone was playing MP and had a crusader that may have broken the quest as well.
I have screenshots of my map but the forums wont let me put links 
halp thanks
The map contains two large areas connected by a narrow pathway. The prisons can appear in both areas. The mark is shown on the map ONLY IF you are close enough. You may need to search both areas to find all prisons.
There are other events that have marks on the map. The mark could be a mark for other event. This screenshot is an example:
There are two marks on the mini map. The upper left (green) is a prison, but the lower right (red) is another event.
If you are not this case, you can post the link of your screenshot as preformatted text using the </> editing tool. Your link will appear like this: https://i.postimg.cc/J4Hh5NNb/Act-5-Rathma-s-Prison.jpg
Bounty is still bugged. Iām standing next to the location on the minimap and thereās nothing on the ground. (Protip: if you see this bounty active, do it first before potentially wasting time on the other four.)
We can mouse over the minimap pins and see which is which. The prisons clearly say ādeath prisonā.
The hover tooltip isnāt captured in screenshots (thanks Microsoft), but thereās little risk of confusion.