Slow speeds with new Spectrum modem - Time Warner Internet

This question is about "Slow speeds with new Spectrum modem", with Time Warner Cable internet and apps. Upgraded to 400 and with new modem download speed was 89. Have had tech out who after 3 hours left and said it was my equipment. Tried again tonight with new modem and router from Spectrum. Speed test before changing was 230 after changing 9! All connections are good. Speedtest was 400 when pc started in safe mode ???

Slow speeds with new Spectrum modem?