I'm getting this error on my NAS. The problem seems to lie with using custom secret keys. I've read the FAQ and a couple of threads relating to this error message here, but none of the symptoms/advice match my problem. The folder sync location is valid and btsync has read/write permission to the folder (btsync creates the various .sync folders successfully). I've also deleted the .sync config files in the folder in case they were corrupt. I've also tried recreating the sync entirely. It only works if I use auto generated keys. I'm posting more details here in the hope it helps isolate the cause. Background: I have several folders on my NAS I'm wanting to sync - all using custom secrets. The first 3 folders in the list work normally - even with custom secrets. Subsequent folders also work if use the auto generated secret for them. However, subsequent folders fail if I apply a custom secret key to them. The custom key is accepted until I reboot the NAS - then the error 'cannot identify the destination folder' is generated (the first 3 folders continue to work normally). I think this is a bug as the update secret dialog accepts the keys I entered. It only gets rejected upon reboot. I don't know if its just coincidence that it liked the first three custom secrets I generated - or if the problem is somehow related to the fact I have multiple sync folders. The FAQ mentions this error may occur if you attempt to reuse the same key on multiple folders. I'm definitely not doing that, each of my custom keys are totally unique (generated with lastpass randomly - they are 60-120 character mixed case alphanumeric strings no special characters). I'm concerned they are somehow being 'interpreted' incorrectly causing the collision described in the FAQ - but I hope its just a case of the config file not being written properly. FYI: I'm using custom secrets because I prefer the idea of variable length secrets. I note in a posting somewhere it says custom secrets are no longer recommended. Any idea why not? Is this just due to fears of user behavior (i.e. generating secrets insecurely)? Any advice anyone can shed on this would be appreciated. I'm using v1.3.105 ARM build on a Synology NAS 213j. It works brilliantly aside from this issue! Many thanks for such a great tool!