Wireless charger malfunctioning?

Background: I have a 2016 Samsung fast charger. I recently started using it for my galaxy s8+ every night to charge the phone until my alarm goes off the next morning. Previously I would use the USB c cable.

Now: The past couple nights I noticed my gs8 has been very warm at its base when I pick it up off the charging stand (the next morning, 6 to 8 hours after placing it on the charger). Upon further inspection, I discovered that it was actually the wireless charger that was extremely warm and was slowly heating my phone throughout the entire night. At the moment I don't think I'll be using that charger anymore and will go back to being wired.

Has anyone else experienced a problem like this? I realize that the charger and phone will heat up while charging, but this was overnight and the phone should have been at 100% for several hours. There is no reason for the charger to be that hot. I realize leaving phones on chargers overnight isn't a huge deal, but they shouldn't be hot that entire time, right?