I have seen similar nighttime persistent lows (a handful of times) and was not able to deduce the reason. Without having it happen a number of times with similar daytime activities then IMHO it is only grasping at straws. I just deal with the issue at hand and don’t overthink the “why” of it. If it happened more often than it would both be more important to understand as well as have enough “data” to really figure out a cause.
[EDIT] Part of this post was moved to How do you treat a bad low at night?