MLW - editing bottom elevation returns error

Hi everyone,
I am trying to change the bottom elevation of a multilayer well (MLW) 
[i.e.,  Steps: 1) select the multilayer well, 2) go to the View Components panel, 3) activate Multilayer Well - Attributes, and 4) activate ONLY the attribute to edit.]
I used this editing process to change its flow rate, that worked.

When changing the bottom elevation, an error message pops up saying "invalid top elevation for multi-layer well creation"
The top elevation is -25, current bottom elevation -230, and I am trying to assign bottom elevation -90.

I selected the top node and also tried selecting the bottom node, with the same error message.

I am using FEFLOW 7.

Please advise.