You've been adding too much baking soda. Have your TA be lower at 70 ppm. Also consider using 50 ppm Borates. Only add acid to get to around 7.5 pH (not below) and let the pH get to 7.8 or so before adding acid. Also, if you have a short pipe run between your SWCG and the pool, point that return more downwards to help dissolve chlorine gas bubbles because if they outgas that will have the pH rise. The hydrogen gas bubbles from the SWCG also aerate the water which increases carbon dioxide outgassing that raises the pH. Having a lower TA target and higher pH target helps reduce that problem.