I have an old Toyota forklift here (S/N: 405FGU25-78696) with the 4Y engine that has difficulty starting quite regularly:
Once every few months it refuses to crank and the operator is met with a loud click noise followed by silence; Presumably the starter gear hitting the ring gear face and not meshing with the teeth.
I have since taken to tapping the starter with a soft mallet or physically rotating the crank in order to get the starter to engage.

Battery voltage is good, and in fact the battery was replaced just in May of 2024.
I have ran an independent ground and positive cable from the battery directly to the starter.
At the time, I removed the starter (Brand new since July of 2024) and inspected all 360 degrees of the ring gear to ensure no broken or damaged teeth were present.
I tested the starter unmounted from the machine and found it worked flawlessly.

The forklift is *covered* in old service stickers telling a story from a previous mechanic that replaced the starter once every 4 months it seems.

I wound up following in his footsteps and replacing the starter in December of 2024 and it seemed to start fantastic for about 6 months. Now in June of 2025 it is suffering from the same issue.

The starters we get are directly from ARPAC ("Performance Advantage" P/N: A000005797), so I'm hoping they're of somewhat quality. Wondering if there is a better long term solution for this reoccurring headache.

Thanks in advance for just reading this wall of text!

UPDATE:
I've since installed a dedicated starter relay, replaced the starter with a better brand name, and have ensured good electrical connections throughout the circuit.
Works flawlessly now, hoping it does so for YEARS instead of months now.
Thanks to all who gave me information and advice!