vacuum reduces when vac pump is isolated

[nike123]

Piezoresistive is also resistor in Wheatstone bridge.

I am confused why pressure sensing piezo elements acting same as thermal conductivity sensing elements (pirani and thermistor).
Are you sure that both types are acting same?

Anyway, I am sure that there is no same vacuum level at all points in system during vacuum pump operation (otherwise there is no movement of contaminants in system), and that some pressure equalization is present when pump is isolated.
Since, in this case, vacuum pump has higher vacuum level than furthest point in system (where vacuum gauge is connected), it is normal for me that, at moment after pump is isolated, all points which are distanced from vacuum pump are at lower vacuum level (higher absolute pressure) than those closer to vacuum pump. And, after equalization of pressures in system, it is normal that at these distanced points vacuum level rise (absolute pressure fall). It could be checked by positioning two vacuum gauges (one at furthest point from vacuum pump and one at closest point to isolation valve. Then we could compare rise and fall of pressures during equalization.