Model :

Hardware Version :

Firmware Version :

ISP :

Using R470t+ v4 load balancer

Setup

WAN 1
Directly connected using PPPoE
No Wifi
Actual speed - 10Mbps
Avg. speed - 8Mbps

WAN 2
Connected via another router (dynamic IP)
Wifi Off
Actual speed - 20Mbps
Avg. speed - 16-18Mbps

LAN
Connected to another TP-Link router for Wifi

PC/Mobile
Connected via Wifi

Case
Both WAN1 and WAN2 are getting their maximum speed in speedtest, download manager and torrent when tested individually whether directly via their own router or via only-one-WAN-at-a-time in Load Balancer
But when using both WAN at once, the speed reaches only maximum of 10-14Mbps, tested via 1Gbps server file download (32 connections), parallel downloads, torrents (VERY HIGH SEED), etc.
Surprisingly, the Load Balancer DO is distributing the download to both the WAN's equally (4-6Mbps each WAN) yet none of the WAN are utilizing 100% of their network when together

Settings
All default, have unchecked Advanced->LoadBalance-> Application-based & Bandwidth-based
Have tried checking them too