I recall seeing that some members have seen examples of penning start high pressure sodium retrofit lamps being responsible for causing ballast failures in mercury vapor CWA ballasts:
“My neighbor tried one in a nice CWA 175 merc I installed for him. Lasted maybe three months and burned up the ballast. Started fine every night, and looked normal though.”
Here is a post that covers this information extensively:
https://www.lighting-gallery.net/gallery/displayimage.php?album=search&cat=0&pos=5&pid=132077