Here is great Flipper rebuild resource.
https://pinside.com/pinball/forum/topic/vids-guide-to-upgradingrebuilding-flippers

Since you were just looking at the flipper rebuild. I would focus their 1st.
1. Check for loose wires broken solder joints. (A little tug). The B-W and RED.
2. Unplug the Jones plug for the flipper and clean.
3. While Jones plug is unplugged check b-w and Yellow continuity Between flipper button and Jones plug
4. While Jones plug is unplugged check b-w continuity Between Jone plug and left flipper coil.

Not related to your issue but can improve flipper strength.
Both flippers RED wire also flows through the Tilt Relay, Reset Relay and Game Over Relay. (See Schematic for wire colors.
Ensure that these are clean and are make a good connection.

Glad I could help. Have fun and play on.