BirdieSync 3.2.1.2 should support Thunderbird 60 64 bits. The error you get is because you use a beta version of Lightning: 6.2 beta 1. It may be necessary to replace this version of Lightning with a gold version: 6.2
You may try to reinstall Lightning extension (it should be available in subdirectory distribution\extensions in Thunderbird installation directory).
Then, I had to go to the Thunderbird profile directory, delete the old extension from the file system, then restart Thunderbird and install Lightning manually from C:\Program Files (x86)\Mozilla Thunderbird\distribution\extensions\{e2fda1a4-762b-4020-b5ad-a41df1933103}.xpi. Restarted and now it works again with no data loss.