electronic liability register Payment

Rupesh Rathi (38 Points)

20 January 2019  
my client had registered as regular tax payer for july-17 to Dec-17. from January-18 he opted for composition. and again from April dealer opted out of composition scheme as he was expecting the turn over might cross the composition limit.
now while filing gstr4 for Jan to mar 2018. error is shown as pervious period liability is pending. while Dec 3b is filed with payment of tax from cash ledger. also gstr4 3b for April -18 is successfully filed. but for may-18 same error is received that pervious period tax liability is pending.
on checking the electronic liability register the amount of 10000 is shown in both cgst and system head.
I want to know what would be the reason for the liability arisen. also how to resolve this problem?