The short answer is that strict adherence to the plan is your best approach, especially if you’re new to structured training…but you’ve already realised that I guess.
Personally, if it was me, I would probably take a week off or just do some Zone 2, and then reset SSB. But this obviously depends how hard you’ve gone so far and the reason I asked about the nature of the extra riding.
If you’re in the 3rd week of a low volume plan and you’ve not completed 3 workouts then, depending on how early/late in the workouts you bailed out, that’s 1/3 of the plan so far that you haven’t completed. Which means you haven’t yet built a lot of base and you only have to repeat 2 weeks.
Note that the plans get gradually more intense, so there’s no point carrying on through the plan if you’re already too deep in a hole of fatigue because it’s going to be hard to climb out of that hole whilst also continuing the plan and building fitness.
Quick tip. If you dont want to give up your TDZ rides then you could consider completing them alongside a TR workout. You obviously won’t be competing and reacting to attacks etc but you’ll complete the event AND get a proper structured workout.