My car is Proton Preve and I have Pioneer AVH-Z5050BT HU installed. Speakers setup is front Adams Digital EMC 650 6.5" mid bass speakers, Adams Digital RUT-28 tweeters, rear stock speaker and Pioneer TS-WX110A underseat active subwoofer. No amp and DSP though, all drove by the Pioneer HU.

I can setup HPF/LPF crossover on the HU. But the TS-WX110A specs mentions the subwoofer has variable LPF built-in (50-125Hz, -12dB/oct) and comes with a remote where I could adjust gain and crossover frequency.
My current setting:
In the HU crossover setting - Subwoofer LPF on (50Hz, -24dB/oct) | Front HPF on (100Hz, -24dB/oct) | Rear HPF on (100Hz, -24dB/oct); I turn the frequency knob on the subwoofer remote to 50Hz
with this setting it sounds nice to me but sometimes the subwoofer will suddenly get cut off and the sound will resume after a few seconds. This happens normally when I am stuck in traffic jam where the car moves slowly.

The wiring is good and voltage are normal when I have the accessories shop foreman checked. He did find my Hitachi NS70L battery not in good health (engine off voltage <12.4V,but still can start engine) so I change to a Amaron Hi-Life 85D23L but the problem still persist.

But when I turn off the LPF and leave the HPF on on the HU, and rely on the subwoofer built-in LPF to work by itself then I don't have this problem and the bass becomes punchy, too much for my taste.
Are the crossover even working as it should when I turn off the LPF on the HU and rely on the subwoofer built-in LPF?