The concept of free transactions has been removed.
High Coin Age Priority transactions would previously be allowed to be relayed even if they didn’t attach a miner fee.
This is no longer possible since there is no concept of Coin Age Priority. The -limitfreerelay and -relaypriority options which controlled relay of free transactions have therefore been removed.
The -sendfreetransactions option has been removed, since almost all miners do not include transactions which do not attach a transaction fee.
-minrelaytxfee can now be set to 0. If minrelaytxfee is set, then fees smaller than minrelaytxfee (per kB) are rejected from relaying, mining and transaction creation. This defaults to 1000 satoshi/kB.
https://bitcoincore.org/en/releases/0.15.0/vous ne pouvez pas outrepasser les rêgles du réseau ... en utilisant "custom", vous ne savez pas ce que vous faites.
et le réseau refuse car lui sait très bien ce que vous "essayez" de faire.
