The speed is cut to Yandex.disk. Why is this happening? Where to look for a problem?

Question

network hardware

Revealed a problem with the speed of the Internet when uploading / uploading to Yandex.disk.
At work, it was always uploaded to Yandex at a speed of 1-3 mb / s. I'm used to it and it doesn't seem too bad. Somehow I had to connect remotely to another PC in my city and transfer 1GB through my disk, and I was a little surprised. There, the download / upload to my disk went at a speed of 8-10 mb / s. I tried to repeat at home. The same 8-10 Mb/s. At work, it’s still 1-3 mb / s, but at the same time, the torrent network in the office quietly accelerates to the prescribed 8-10 mb / s. Everywhere providers are different, but the connection is the same 100Mbps.
I tried to make tracert - at home and at the client it showed some numbers. In the office, it showed < 1 ms to the first router, and immediately after it showed asterisks.

The network at office is arranged so.
Comes optics, two pieces. Next is TP-LINK TL-R480T + combining everything into one channel. Because Since this router has a port forwarding limit, it has a demilitarized zone configured on it, into which the "last" TP-LINK TL-R600VPN is already connected, in which all the necessary forwarding for various needs is already configured. Tracert up to R600VPN shows <1ms, it doesn't see anything behind it.
I suspect that somewhere in this bunch of routers, the connection to the disk is being cut.
Tell me what settings you need to look for and check so that the "office" connection status rises to "home"?

Z.Y. The zoo of routers is connected with the fact that there used to be one dead channel for 10 Mbps per legal entity and everything worked / was configured through R600VPN. Then they threw a cheaper second channel at 100 Mbps and bought the 480th to organize balancing. And they left the old router, because the 480th is limited in "forwarding" and everything is already set up on the old one.