unwrap() command resulting in phase bump

I have raw phase and gain data where the phase data wraps at 90deg (expected). When I tried to unwrap the data for plotting I noticed a "bump" in the phase that did not seem consistent with the phase trajectory.

% Unwrap the phase data
phase_deg = unwrap(phase_deg, 90);

I then manually unwrapped the data at 90 degrees and the result is what I expected from unwrap.

% Unwrap the phase data
    if(phase_deg(ii) > 90 )
        phase_deg(ii) = phase_deg(ii) - 360;
    end

I'm not sure what I'm misunderstanding in how to use unwrap, or why it is not handling my data as expected.

See image below for the data: