Bionavis MP-SPR VASA 210A- Reference channel sensogram not completely flat

Hello,I am currently using the Bionavis MP-SPR VASA 210A instrument with a gold sensor functionalized with carboxylic acid-terminated thiols, which we use as a platform for assembling small molecules.We have two channels, one we use for reference and the other for the injection. When we inject our small molecules, we consistently observe a smaller but otherwise very similar increase in the sensogram of the reference channel, following the same trend as the main injection channel.We are using parallel injection, and the reference channel is set to “None,” meaning that only running buffer should be flowing through it. The flow rate is 30 µL/min.I'm unsure what might be causing this behavior. If anyone has encountered a similar issue or has any suggestions about possible causes, I would be very grateful for your input.Thank you in advance.