This is likely an accuracy issue, The aspect ratio difference is a primary clue.
Warning: changing accuracy can have unintended effects and failures. I suggest saving your work BEFORE the change, Test everything (including merges and references) before saving. Make sure you can get back to where you were before the change just in case it becomes a major headache!
Go to File - Prepare - Model Properties - Accuracy.
If you are set to Relative accuracy and you don't want to change to absolute, try lowering the accuracy value under the "change" option. For high aspect ratios, relative accuracy may be the primary problem (long length, thin part as you describe).
You can change the accuracy type from Relative to absolute, which i believe is more appropriate for your situation. You may also need to reduce the value there also.
You can learn more about accuracy by searching the community. There are LOTs of good posts on how it works and what it does.
