This seems a particularly difficult battle to understand. I have Sumption and DeVries who seem at odds with each other.
It seems most likely to me that the pits only covered the front of the archers. Perhaps the French are in 4 battles? 1 mounted charges the English Man at Arms and is thrown back, in part due to the fire of the archers on their flanks. Battles 2 and 3 (also mounted) attack the archers and are discomfited by the concealed pits and ditches and make no progress. The 4th, perhaps mainly of foot, flees the field.
Any other sources or suggestions?
The curiously structured wikipedia article on the battle has, I think, four reconstructions compared, which is worth a look. Also, check out Tout's version on De Re Militari (https://deremilitari.org/2014/07/the-tactics-of-the-battles-of-boroughbridge-and-morlaix/)
Personally, I'm not convinced the first attack was by cavalry. The attackers were Bretons, but it isn't clear whether they were men-at-arms or light infantry (Breton bidauts being a common troop type of the time). So, one might suggest a bunch of infantry skirmishers confronted by longbow archery didn't get far enough forward to spot the pits. Or, if they did, they didn't relay the information to the men-at-arms (perhaps speaking a different language or just because no self respecting French man-at-arms is going to listen to a light infantryman).
Have we this battle in the wiki library thread here?
It might make a good article comparing the narratives too
Are there any other battles of the period where Breton Light Infantry played a significant role?