Get checked: Over time after an ablation some of the lining of the uterus can start to grow back resulting in spotting or bleeding. However occasionally there can be a problem to get it checked out. This is not uncommon: It is not uncommon to have some bleeding after an endometrial ablation.

https://www.healthtap.com/questions/537812-i-had-a-uterine-ablation-10-years-ago-i-have-recently-started-spotting-dark-brown-blood-and-what-lo/