Metoprolol IS an anti-arrhythmic drug. It is commonly used for arrhythmia control. That doesn't mean it doesn't have side effects. Everybody is different. If you are experiencing and increase in symptoms you should talk to you doctor. I am assuming it is an EP as they are the only type of cardiologists really qualified to treat rhythm problems. After 8 months of control and a break through like you describe I'd contact my doc. No one here can diagnose what you are going through and what the problem is much less how to treat it.
Most of us do not understand what are P, R QRS and other complexes and waves. ECGs are very complex to understand. Multiple things can happen at one time. Sorting them out takes a specialist. I will link a few articles designed to simplify the descriptions of these problems for the average layman to help understand these problems. See https://my.clevelandclinic.org/health/drugs/22867-what-are-antiarrhythmics
Note : from that article "Class II, beta blockers: These drugs slow down the heart rate, often by blocking hormones such as adrenaline. Examples include acebutolol, atenolol, bisoprolol, metoprolol, nadolol and propranolol."

SVT and and PVC are very different.
See this for a good description of SVT and treatment options. https://my.clevelandclinic.org/health/diseases/21800-atrial-tachycardia#:~:text=Focal%20atrial%20tachycardia%3A%20This%20type,can%20resolve%20multifocal%20atrial%20tachycardia.
Here is a link to what a PVC is https://my.clevelandclinic.org/health/diseases/17381-premature-ventricular-contractions.