My experience has been the same as yourself. It only seems to be on TSN2 and I only notice it when viewing F1. I suspect it is something to do with the video source, that TSN is sourcing for the race, in combination with the particular transponder that Shaw Direct is using.
Friends and relatives who are using Telus Optik to record F1 are not seeing this ongoing artifact. It is strictly with Shaw Direct to my knowledge.