Infiltration for spying or comraderie sabotage is bound to happen in these WeChat groups when money is involved.
Screening process as group head (群主) endowing banning privileges is at one's disposal. Over time, the real owners will differentiate themselves from infiltrators. The branching out to a separate subgroup for private discussions with regulars who've earned their badges would naturally occur. The main Wechat group would intentionally be kept. Strategic ambiguity and misinformation would be released to previous discussion group to mislead prying eyes.
In the good, the bad, and the ugly analogy, Junfa and developers like Vanke are among "the good." Positioning themselves as the more responsible companies, they'd try to maintain positive after-sales koubei as one of selling points for long-term competitive advantage in the housing market. They may address plumbing and flooding within the residences' apartment, even as warranty period (房屋保修期) expires after the post-delivery window.
If newer phase development is ongoing, beyond the current unsold apartments, developers and their property management arms would capitulate more to owners' complaints. Inspections pending need to be passed, so developers in these situations may bend further to be in local governments' good graces. Making complaints to 经开区 have more bite in these circumstances.
As long as potential customers' beaten path to the 样品屋 show room is beautified, lesser developers focusing soely on near-term transactions wouldn't bother fixing internal problems unseen by unsuspecting buyers strolling into premises with cursory glances.
In older compounds where projects have been completed, summoning 市长热线 （mayor's office) in some cases wouldn't be enough to pressure the bad and the ugly ones to right their wrongs. Tough ordeal hunting down companies that went under.
Perhaps 诉讼 (litigation) would be an option if all else fails. Legal fees in Yunnan are much cheaper than those in Shanghai, but would increase incrementally per owner/client participation.
Rowdy demonstrations by owners are less favorable these days, though a last resort for older generations. Being a foreigner involved in these ruckus may spare you from a local police arrest if push comes to shove during an all out protest. Locals are treated more harshly than foreigners in the event authorities come to shut down the "social unrest." Testing this out is probably not recommended in these volatile times.