If these are Windows hosts, it is probably the Windows Firewall, that by default, will block pings from “other” subnets than it has interfaces in.
Google allow ping from other subnet windows
Here’s one simple, but not very specific way Configure the Windows firewall to allow pings
For more granular control see this post.
YOu mean besides being on different subnets and different bridges… and with no view into the firewall rules???
In firewall not rules
In post not details
I’m gonna start calling you Yoda. 
It can best be summed up by the monologue…
https://www.youtube.com/watch?v=Mzfc9rjow9g