Lingering transmission rate limit?

Using OpenWrt on a router that uplinks via wireless to my phone's wifi hotspot as I don't have home internet. I have laptops and such connected to the LAN side of the router. This setup had been working without issues for at least a month.

My monthly usage is metered and when it maxes out the download rate gets cut to around 50KB/s.

Attempting to make things run a bit more smoothly under this limit, I installed the package luci-app-qos and set the maximum download rate to 50KB/s (I think?).

Something weird happened and I became entirely unable to access the internet from devices on the router LAN.

I uninstalled luci-app-qos, along with the tc package it had installed, and things seemed to go back to normal.

My monthly usage has reset and now the phone itself is able to access the internet at full speed but my LAN devices are still limited to 50KB/s.

I've tried reinstalling luci-app-qos in order to change the average rate, but now I get an error message whenever I try to install that package:

root@inlet:/etc# opkg install luci-app-qos
Installing luci-app-qos (git-20.221.53167-304ad04-1) to root...
Collected errors:
 * satisfy_dependencies_for: Cannot satisfy the following dependencies for luci-app-qos:
 *      kernel (= 4.14.171-1-b84a5a29b1d5ae1dc33ccf9ba292ca1d)
 * opkg_install_cmd: Cannot install package luci-app-qos.

I've verified that both the tc and qos-scripts packages are uninstalled (as reported by opkg info). However, iptables is installed. Is it possible that the qos scripts set up a configuration for iptables which is still active? Where is iptables configuration stored?

After rebooting my phone, the issue has gone away. Would still appreciate advice on how to get qos installed.