Question Regarding Send_to_many function of blockchain wallet api I am using send to many function of blockchain wallet api and i am facing issue.

when upto 20 transaction done then after i get error in terminal that 

1538652825520 - error: ERR_PUSHTX

1538652826930 - error: ERR_PUSHTX

and until that upto 20 transactions get 1 confirmation on block i am unable to send any other transaction from that wallet and it's specific address. 

i want to use sent to many function for sending unlimited transaction from one wallet to my site users bitcoin addresses when they submit payment request from their account.

kindly help me regarding this. 

Thanks
What you need to manage is the fee rate. Bitcoin core nodes will not relay transactions (or include them in blocks) below the minimum fee rate of 1000 satoshi/kB (-minrelaytxfee), so if you keep increasing the transaction size, but not the fee, you risk not getting relayed or even mined (-blockmintxfee), since miners typically maximize the fee rate in the block being mined.