Sudden onset severe stutter in 4.5 year old boy

Sudden onset severe stutter in 4.5 year old boy New here, I am not sure where to ask this question I have not found a similar experience anywhere and the pediatrician and the speech pathologist are stumped. At the beginning of April my 4.5 year old started overnight with a severe sudden onset stutter that continually got worse over about 10 days culminating in about 48 hours where he was having 10-30+ repeats and stuttering through most words in most of his sentences. Then overnight, it got much better but did not resolve completely. He has some concerning signs, during the most severe stuttering there was obvious signs of frustration: yelling, hand gestures, face scrunching, reddening of the face, etc. It then calmed down for about a month or so where he was just 3 or so repeats mostly at the beginning of statements but sometimes in the middle too. He recently had strep on May 28 and when he was sick the stutter was fine but 5 days into the antibiotic course his stutter started to get worse again and has only worsened since then and has now been since Friday nearly as bad as it was during his most severe episode in April. He has been with a speech pathologist for about a month now and we can't find any patterns, she's as stumped as I am and were are desperate for a neuroevaluation but our neurologist appointment isn't until 9/3. I guess I am just looking to see if anyone has experienced anything similar.