Sharp Peak at Start of Injection?

Hello, I am currently doing some optimization on a lower resolution SPR before running this experiment on a Biacore. At the start of my injection, I see a sharp peak followed by immediate signal increase (shown below). Is this likely due to a buffer mismatch?

To give some more details if needed, I am looking at an association between a protein (40 kDa) and other large macromolecule (40 kDa) that is expected to form a complex. It is unclear how slowly dissociation would occur so we would most likely just be able to view the association phase by SPR. Immobilization went as expected because of pH scouting and the running buffer was sodium acetate with 100 mM NaCl (pH 5.1) (used HBS for immobilization on a carboxyl chip). I know this isn't the typical running buffer used but it is what is experimentally relevant for this situation

Hi,
When you have the same with a buffer alone injection, it is something from the injection system.
Normally a buffer mismatch (flow buffer / analyte buffer) is only visible during analyte injection.
Is this a reference subtracted line?

Arnoud