Coupon email title is gibberish

As the title says, after the wheel has been spun and a coupon was rewarded, the email sent has insanely long titles such as:
=?UTF-8?B?15bXm9eZ16og15HXp9eV16TXldefINeb15PXldeo15kg16nXlden15XXnNeT?= =?UTF-8?B?INeR15zXmdeZ15gg16DXmdeZ15gg16TXodeY15Qh?=

no matter where i try, i can’t seem to change the emails titles and those long titles 100% go to spam every time. I probably missed something.

please help!

besides that, everything works as intended, I just need to get this email titles sorted out.

Thanks!