NVIDIA GeForce 551.68 driver addresses NVENC issues for Turing cards
The company discovered a problem with the latest Game Ready driver that may result in corrupt encoded videos.

Users using the GeForce GTX 1630, GTX 1650, and GTX 1650 Ti for video encoding through the NVIDIA NVENC encoder are urged to update their drivers. NVIDIA has identified a bug in the latest 551.61 driver, which could lead to video corruption or errors during GPU encoder utilization.
This driver doesn’t introduce any additional fixes or enhancements, and should be downloaded and used only by those have those cards and use them for video encoding. Others should definitely wait for the next WHQL or Game Ready release that will undoubtedly incorporate this fix regardless.
The GTX 16 series utilizes the 6th generation NVENC encoder, which supports H.264 and H.265 video encoding. It lacks support for AV1 encoding as found in the 7th Gen NVNEC in Ada GPUs, though. Worth adding that GTX 16 series still supports up to 8 maximum concurrent sessions. The increase from 3 to 8 concurrent sessions was a result of a recent NVIDIA’s collaboration with Twitch , which enables multi-track video streaming.
Source (and download): NVIDIA