Time and time again when building new SQL servers I see this issue come up.
The Veeam KB article kb2027 does not indicate the second two registry keys which I think may be important here.
That KB article only references SqlExecTimeout
I think its important to get that article revised to also mention SqlLogBackupTimeout and SqlConnectionTimeout.
Also I don't know if things really changed in 9.5, but we do not have a veeam entry in the Wow6432Node tree in the registry. I'm not sure if it matters but I created one. The tree in HKLM\Software is also spelled "Veeam" Not with a mis-placed capital M at the end. I'm not sure it is case sensitive in the registry or not, or maybe that was a small bug fixed recently.
Anyway I think Veeam should trigger on this error and try to give SQL more time. Sort of make this an automatic tuning process like TCP window scaling or any other computer feature that does on the fly adjustments to operating parameters to keep an optomized threshold. Veeam is great but as long as people write software and people are not perfect, there will always be issues - not really Veeam's fault, but SQL, which maybe Microsoft should write an API that says "Hey Veeam hold on, I'm still working on the transaction logs, I'm 50% done and I estimate I will be another 14 minutes..." then Veeam could say "Ok I'll wait and do something else awhile". But that level of AI is probably beyond the scope of this forum.