Are you running them with the smoke on? Try turning it off.
When you say "Every time this occurs, I test the areas where these locomotives slow down ...."
You test them after running with your meter. Do you have any transformers with amp and volt meters built in? Can you borrow one or install meters?
What gauge wire goes to these blocks? how long is it? how are they connected to the tracks?
how long are these blocks and how many joints?
what type of track are you using?
What type of power?
Does your Lionel engines that run fine, include newer larger steamers with chuffing smoke?
