To do it properly I would say take the whole ridge off and put new cement either side and then point it up.

the sections that have fell through need re bedding in, as re pointing may only solve the issue again for a short amount of time re bedding the section will maintain/prevent it from potentially happening again

Ashley

You would need to remove the ridges and re-bed them an change any that are broken

If you hack out loose and repiont the rest of the old mortar will fail at some point in the near future and will need attention so by getting them all lifted cleaned off and rebeded there should be no maintenance for many years also look at dry ridge systems or flexim ridge putty

Hi there , I personally would remove and re bed the ridges to ensure a good water tight ridge line . Also the next best option would be to go for a dry ridge system to ensure the ridges are fixed safely and would need no maintenance in the future if done correctly