Four of their five starters are injured/unavailable this week.
I wouldn’t draw conclusions that something is horribly wrong in the OL room based on four games (after an encouraging preseason). I went back and watched Brown during the preseason and although his snaps were limited, he looked good and I didn’t see any effort issues.
There’s a lot of season to play and this week is a bit of a fluke for obvious reasons. If they show no improvement over the season and mistakes aren’t corrected, then there may be grounds to speculate that something is seriously wrong. Even then, maybe Popovich is a good coach and his return will help next season.