Wow – thanks, all, for the great information!
Because our problem site is relatively inconvenient to access, I think on our (@jlemontu-org ‘s) next visit, he’ll come armed with a number of options. We’ll pick up a Taoglas antenna, as well as bring along a spare Pulse antenna, in case the existing one is compromised. And we can experiment with different antenna positions relative to the other conductive components in the enclosure. Perhaps it makes a difference which plane the antenna is oriented in as well.
Really appreciate you all sharing your wisdom! (and I love the photo of your workbench, Sara!)