The pressure difference fluctuates back and forth when the load on the purification tower becomes too high

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After the unit’s capacity was increased, the feed load to the distillation tower became too high; the feed to this tower consisted of a nearly pure component, 99% C8, with toluene and non-aromatic compounds being removed from the tower top. The material at the bottom of this tower is used as a heat source to heat the feed; frequently, the tower pressure decreases or increases (the pressure difference either grows or shrinks), which disrupts the equilibrium. There is an air cooler at the top of the tower serving as a condenser, and the flow rate is automatically controlled based on the temperature at the top of the tower. When the tower pressure drops, the temperature decreases after cooling; the liquid level at the bottom of the tower falls, causing the material to rise upward. The liquid level in the reflux tank increases, while the opposite occurs when the tower pressure rises. I wonder whether it was flooding caused by excessive tower load or a temperature change after cooling – I can’t tell which is the cause and which is the effect. There is another scenario in which the backflow increases, the tower pressure rises as well, and the temperature after cooling goes up as well; it is suspected that the load is too high, creating a sort of vicious cycle. I’d like to ask everyone: what could be the reasons for this situation, and how can I adjust it?