running check-fetch-times.php?show=versions indicates you do need some script updates to the template set. There’s a newer include-wxhistory.php V1.11 amongst them. Please do the update(s) and see if that resolves the error with wxhistory.php – if not, I’ll take a deeper look 
Note that some of the updates needed address issues with PHP 7+ as the older scripts used features/functions that are now deprecated in PHP7.