I had 3 disputes with Aliexpress sellers in quick succession. All 3 were solved within 48 hours without Aliexpress getting involved, but they were all under $15. From what I have heard, Aliexpress is trying to attract western buyers, where as they have a flood of Chinese sellers, so tend to side on the side of the buyer, and sellers know this.
If its not your life savings, and the seller has a couple years to their name, I'd feel fairly safe.
eBike: Q100H on 16S with Phaserunner FOC Controller
eMotorscooter: Vectrix VX-1 on 36S
eCar: Mitsubishi Outlander PHEV... Waiting for warranty to expire
eHouse: Still on grid, but with LTO batteries and 3kw LF inverter...
After 5 builds, the best advice I can give, is start with high quality products. I prefer http://www.ebikes.ca