Tencent Holdings Ltd.’s shares are dangerously close to falling below a key support level.

The biggest stock in Asia fell 2.3% in Hong Kong despite no immediately apparent trigger. Theories circulating around some trading floors included souring sentiment from investors in China as well as concern that Tencent’s decision to air National Basketball Association games may backfire.

The stock closed at HK$320, a level that has provided a floor for declines on three occasions this year. The stock’s successively smaller bounces off that level suggest the support is at risk of breaking. Shares traded above the line for most of the session before briefly breaching it in the afternoon.

Tencent decided to livestream NBA games starting Wednesday, putting it at odds with a decision from China’s state broadcaster to stick to a boycott. Tencent also drew the ire of Hong Kong when Blizzard, partly owned by the company, banned a gamer for endorsing Hong Kong’s pro-democracy movement.

Mainland-based investors Monday and Tuesday sold a combined net $54 million of Tencent shares through trading links with Hong Kong, according to the city’s exchange data. The stock has lost almost 20% since its April peak, with three weeks to go before the company reports quarterly results.