Check your gas flow through the contactor, is it steady, at high flow rates the amine will tend to be held up in the tower and once flow drops the level in the tower will fall down which will accumulate in the bottom of the tower which will present itself as a high level an call for the level control to dump more out. Another cause of level flucuations in the tower is caused by amine foaming caused by dirty amine or high level of condensate in the amine. This erratic flow rate to the amine still can cause changes in the level and pressure, especially if you have hydocarbon contamination. Take a sample of both rich and lean amine and send it to a lab to get it tested for contamination. I worked in a plant with an amine system, the contactor was foaming so bad it carried out amine with the gas, tried using anti-foam (Band-aid solution) ended up changing filters more often, eventually no more foaming problems.