I found the same problem in SER6 Pro 7735 HS, the unit had maybe 1 month after it was manufactured and the compound was already solidified. I didn't like the temps so I decided to change to TG Kryonaut.
The thermal paste is Phase-change silicone grease.
When the PC is hot, the thermal paste will become soft as paste,
it will get hard when the PC cools down.