The WFCO is a 3 stage charger. Just not a very good or reliable one.
There is no situation where that WFCO should put out less than 13.2V. If it is, best get a replacement on order.
Still think you should fully charge and load test that battery. Using a different charger perhaps. But you're running out of time to get off the stick and replace that converter.
We can help you select a replacement, if you can shoot a photo of your existing one. Your description above makes me think it might not be built into your load center. So the links I gave you above might not be correct.