Since GYD9E is not an industry-standard part number (like 2N2222 or LM317), you won’t find a datasheet from a single manufacturer. Instead, use this article as your reference. However, for the inside the GYD9E, download the official STMicroelectronics L298 datasheet (Rev 14 or later). It covers all electrical specs, timing diagrams, and application notes.
If your motors stop abruptly while VMS is still present, allow the module to cool. gyd9e datasheet