Now. We've mined about 65 blocks with a legacy address earlier.
Transactions are failing indeed......
Any way we can get in touch to see if there's a way to recover these coins ?
The legacy addresses can exist, though they are not supported officially (and won't be supported).
In the example above, transaction from older address succeeded, but officially such transactions
would be declined with updated nodes. That's why in the future such mechanics won't work and
it's very strongly advised to not use any legacy addresses.