Bubbles in the sight glass and a rising hot-gas temperature are clear signs that something in the system isn’t running the way it used to, especially for a heat pump with this many hours on it. What you’re seeing usually points to a low refrigerant charge or a restriction somewhere in the circuit. A sticking expansion valve can definitely cause this, because it starves the evaporator and forces the compressor to work harder, which pushes the hot-gas temp up. Low refrigerant will create almost the same symptoms.
A failing compressor is possible, but it’s usually the last thing on the list, scrolls tend to show noise, vibration, or poor pressure differences before completely giving up.
Service will probably check the charge, test the valve, and measure the pressure conditions. With a unit of this age, you might be dealing with a leak or a part that’s simply worn out. The good news is that the symptoms you describe fit common, fixable issues rather than a total compressor failure.