Slow (synology quick connent to) speeds

My (synology quick connect to) speed uploading to my offsite synology S220+ plus were running about 1.5 MB per second over the past year. last week i updated to the new firmware and the speeds to the nas were running 21 MB per second. this week they are running 500kBs. my internet speed where the nas is located is 300 MB down 300 MB up. The location where the computer is that I am uploading from the PC is 500 MB down 300 MB up. Both are hardwired . No other changes to computer/nas. any suggestions plesse? ps I am getting approx 4MBs from my phone (wifi) when using the app on the same network as the computer in my office (off site from the NAS & not through synology quick connect).

Update. Synology mysteriously now loading at 21MB/s again.