Most visitors online was 1660 , on 12 Dec 2020
A photo of what you have there would help, mainly the movement.
Your symptom is a very common one. It's often caused by a worn escapement.
Most of the time the flaw can be corrected (temporarily) by moving the pallets slightly closer to the escape wheel. The escape wheel teeth MUST always drop onto the slightly curved upper (dead) faces of the pallets.
The "beat" on your clock would most likely be set automatically.