Since when do you have interference in UL ? Since forever ? Or since a specific date ?
When you swapped the two cells, does the problem occur on the same “physical sector” than before, or on the same “logical cell” than before ?
If same physical sector – then you have a HW issue with the micro BTS. Check feeder connection and try to make a full restart of the BTS.
If same logical cell – then you do have a configuration problem, probably due to frequencies. Could you swap frequencies from one cell to the other one?
For each cell :
* What is the HO UL Qual % in each cell ? (busy hour value)
* how much is the TCH erlang BH traffic ?
* how much is the “idle channel interference” ?
* how much is the average timing advance ? (in NPO Indicator family – Radio Measurements -)