Duh, think I figured it out. Here's the DVR log:
ffmpeg: ch508-dANY-20eda3055847-remux: [h264 @ 0x934dfc0] sps_id 0 out of range
2023/05/09 14:09:50.319032 [HLS] ffmpeg: ch508-dANY-20eda3055847-remux: Last message repeated 1 times
2023/05/09 14:09:50.319048 [HLS] ffmpeg: ch508-dANY-20eda3055847-remux: [ac3 @ 0x934ec80] Multiple frames in a packet.
2023/05/09 14:09:50.636851 [HLS] Probed live stream in 637.690607ms: h264 1280x720 progressive 2934414bps
2023/05/09 14:09:51.713194 [ENC] Starting encoder for ch508 in /volume1/DVR/Streaming/ch508-dANY-20eda3055847-1574841366/encoder-1-1365697251 at 1 (0.948433) (encoder=hevc_vaapi, resolution=384, deinterlacer=blend, bitrate=572, segment_size=0.01)
2023/05/09 14:09:51.794103 [HLS] ffmpeg: ch508-dANY-20eda3055847-1-hevc-aac-copy--572-64-384-0-0--blend-false-false-0.01-0: Error while decoding stream #0:1: Invalid data found when processing input
2023/05/09 14:09:51.815543 [HLS] ffmpeg: ch508-dANY-20eda3055847-1-hevc-aac-copy--572-64-384-0-0--blend-false-false-0.01-0: Error while decoding stream #0:2: Invalid data found when processing input
2023/05/09 14:09:51.958975 [HLS] ffmpeg: ch508-dANY-20eda3055847-1-hevc-aac-copy--572-64-384-0-0--blend-false-false-0.01-0: [hls @ 0x8c557c0] Stream HEVC is not hvc1, you should use tag:v hvc1 to set it.
I turned off "Use HEVC for transcoding" and seems to be working again...think that got turned on inadvertently at some point. Thanks for help!