And assuming you wiped everything down good before drawing, no cross contamination etc. It shoulda been harder to push if it was plunger related, thats my experience anyway working with straight solvents and even EO. EO will get one fairly quick but the next day you are not budging that plunger...BB would be making the barrel itself look different too from what I recall (I am for sure doing some more testing on this).
Now if it were in my hands and knowing how I am I would be getting to the bottom of it. Drawing up a half cc of each compound and seeing how it goes along with a mixture...then going on into microbiology and doing agar plates on it (if you wanna do that I can let you know how to prep out some homemade plates to see if anything grows)