They are currently using the PL-96 which by most accounts available online is an upgrade of the licensed produced D-30.
What was upgraded is really vague beyond increased range and guided rounds capability (lighter construction material?) but they did mention the gun was backwards compatible with Russian 122mm ammunition but whether the rounds specifically developed to be used with the PL-96 is backwards compatible would need more information.
If the above mentioned information is true, the Chinese must have increased the power of the charges to increase the range. The increased chamber pressure must have tore the older Soviet made guns which have been rated for a lower pressure especially considering the number of rounds they have to fire a day.
Looking at that muzzle brake in the 2nd video, I have seen guns 40 years old that don't look like that.
It looks like it came from a 17th century blacksmith.
Do we believe those ranges quoted on the internet? If so, the base range of PLZ-07 is 18km and 2S1 are 18 and 15 Km respectively, so it would check out that the charges are more powerful than the original Soviet spec. Since Pakistan is only using Chinese-origin equipment in that caliber, there is no reason to follow Soviet specs.
In actuality, then the quality of the Pakistani ammo is probably quite good because it is actually creating that higher pressure.
The solution is quite simple since the ammo is two-piece, don't fire at full charge (all bags).
Also adding, Pakistan is not using 152mm ammo as used by 2S3, so I wonder if that second tweet is accurate.
152mm is not listed here