I just started tslim and not having these problems, but I did setup tslim with slightly higher basal rates.
One thing I noticed is that after tslim suspends, and resumes, then I might see a bigger rise than expected.
Are your highs after meals? Check your pump setting, and maybe adjust.
Have you used T;connect to download and review how the pump is changing basals?
Can use on computer or phone. I find it very helpful, and look at phone instead of pump to review.