No, this is a problem with the live weather (it started happening even before SU5). The ATC doesn’t seem to be following the standard 29.92 inHg or 1013 hPa altimeter past the transition altitude, they’re still reading the surface barometric pressure at each ‘weather blocks’ as you fly through.
The thrust problem is also caused by the Live Weather issue. Where the temperature can become insanely high on climb and cruise through some of these weather blocks. The temperature affects the air density choking your engines and your wings making your aircraft having trouble climbing and keeping altitude.
As of this moment, use the Custom Weather Presets with a standard barometric pressure and temperature that the ATC will use the whole flight. Then you won’t have them constantly bothering you with expedite and will stabilise your aircraft.