Flecanide

I had a SVT cardiac ablation a month ago. This first week was rocky but I had started feeling better. Since the ablation I have been taking flecanide and diltiazem. I had been feeling much better until yesterday. When I went to the grocery store I had gotten dizzy, came home and layed down and felt better. Later in the night I was just sitting down and I go what the er dr described as disequilibrium very bad. My BP went to 141/109 and my Apple Watch ecg was fine. I went to the ER they did a 12 lead and blood work everything was normal except my potassium was slightly low. I still felt bad my pressure was still elevated but after an hour it went back to normal 117/72. The ER doctor came to the conclusion that it was the flecanide. I asked if that was possible since I have been taking it for a month and haven’t experienced that before and he said that it can happen later because it builds up in your system and to talk with my EP. She said that it is not the flecanide because I would have gotten it when I first started taking it. So I have no idea who is right. She also said she highly advises that I don’t lower my flecanide dose for at least another month. Has this happen to anyone getting side effects a whole month after? I don’t know who is right my ep or the er dr….