Unfortunately, I’ve now experienced the same failure on another system. This one has decent hardware and I was just rebooting Windows. After doing so, Syncthing fails to start with the same error as on the other device.
[start] 2025/03/25 13:53:49 INFO: syncthing v1.29.4-rc.1.dev.118.g7a475169-tomasz86-v1.29.3-sqlite "Hafnium Hornet" (go1.24.1 windows-amd64) tomasz86@tomasz86 2025-03-24 21:19:38 UTC [noupgrade, stnoupgrade]
[start] 2025/03/25 13:53:57 WARNING: Error opening database: init database: runscripts (UPDATE indexids SET sequence = (
SELECT COALESCE(MAX(remote_sequence), MAX(sequence)) FROM files
WHERE files.device_idx = indexids.device_idx AND files.folder_idx = indexids.folder_idx
)): NOT NULL constraint failed: indexids.sequence
[start] 2025/03/25 13:53:59 INFO: syncthing v1.29.4-rc.1.dev.118.g7a475169-tomasz86-v1.29.3-sqlite "Hafnium Hornet" (go1.24.1 windows-amd64) tomasz86@tomasz86 2025-03-24 21:19:38 UTC [noupgrade, stnoupgrade]
[start] 2025/03/25 13:54:04 WARNING: Error opening database: init database: runscripts (UPDATE indexids SET sequence = (
SELECT COALESCE(MAX(remote_sequence), MAX(sequence)) FROM files
WHERE files.device_idx = indexids.device_idx AND files.folder_idx = indexids.folder_idx
)): NOT NULL constraint failed: indexids.sequence
[start] 2025/03/25 13:54:05 INFO: syncthing v1.29.4-rc.1.dev.118.g7a475169-tomasz86-v1.29.3-sqlite "Hafnium Hornet" (go1.24.1 windows-amd64) tomasz86@tomasz86 2025-03-24 21:19:38 UTC [noupgrade, stnoupgrade]
[start] 2025/03/25 13:54:11 WARNING: Error opening database: init database: runscripts (UPDATE indexids SET sequence = (
SELECT COALESCE(MAX(remote_sequence), MAX(sequence)) FROM files
WHERE files.device_idx = indexids.device_idx AND files.folder_idx = indexids.folder_idx
)): NOT NULL constraint failed: indexids.sequence
[start] 2025/03/25 13:54:12 INFO: syncthing v1.29.4-rc.1.dev.118.g7a475169-tomasz86-v1.29.3-sqlite "Hafnium Hornet" (go1.24.1 windows-amd64) tomasz86@tomasz86 2025-03-24 21:19:38 UTC [noupgrade, stnoupgrade]
[start] 2025/03/25 13:54:17 WARNING: Error opening database: init database: runscripts (UPDATE indexids SET sequence = (
SELECT COALESCE(MAX(remote_sequence), MAX(sequence)) FROM files
WHERE files.device_idx = indexids.device_idx AND files.folder_idx = indexids.folder_idx
)): NOT NULL constraint failed: indexids.sequence