Bad reference for TCs

TCS
Travers Smith
#1

I applied to 27 TCs so far and have an assessment day next month with K&L Gates after having been rejected after a first interview at Travers Smith in March. I am now quite worried about getting a good reference from my current job as I was told today I was having my probation extended by a month, despite mostly doing quite well but because of one mistake that my department head had a meeting with me about and where I wasn’t really given a chance to explain myself properly. Does anyone have any experience of previous employment references coming back to bite for TCs?