Possibly, but a simple “I don’t recall” or “now that I think about it, I was wrong before” will take care of that. Witnesses change testimony all the time with no consequences. I worked IT for law firms for quite a while and this is something that would frustrate lawyers and blow up cases occasionally. Courts recognize that testimony is “to the best of your recollection” In reality, perjury charges are extremely rare as courts do not want witnesses to be afraid to testify.