I've purchased the ER-605 router two months before for load balancing multiple internet connections. I have an optical fiber connection (100 Mbps up and down) and two 4G connections ( 15-40 Mbps up and down). The upload speed with ER-605 is only 10-20% of the download speed. If the download speed is 130 Mbps, then the upload speed is only 13 Mbps. Please find the attached screenshot and the speed test results link.

I've used the AX-73 router in the past, and the download/upload speeds are almost the same. Could you please check this or arrange technical assistance if it's a configuration problem?