580K Cummings Diesel Start problems

Hi everyone! We have a 1988 case 580k Cummings diesel with a starting problem. Replaced OEM starter about 5 years ago. 580 ran flawlessly for about 3 years then wouldn't start. Replaced starter again with OEM and ran flawlessly till now. Batteries measure fully charged, voltage drops look good, but it looks like bendix gear is extending but not fully engaging fly wheel and appears the gear is collapsing the spring on the bendix shift, possibility contacting the fly wheel? Any suggestions...

580K Cummings Diesel Start problems