MIDI regions consist of X letters

These are SysEx data. Maybe your external MIDI controller is sending them out while you are recording.

Open the Event List (make sure the blue Syst. Exclusive Button is enabled) and you should see those Events. I

If you don't need them, select them and hit delete.

Tip: If you have a lot of other data (Notes) going on, select one of theses SysEx in the list and choose Edit ➤ Select ➤ Similar Events to select only those and then press delete.

To avoid the recording of any unwanted MIDI Events from your external MIDI Controller, go to the Project Settings ➤ MIDI ➤ Input Filter and select the checkbox for any MIDI Message that you don't use (i.e. Program Change, SysEx, etc.)

Hope that helps

Edgar Rothermich - LogicProGEM.com

(Author of the "Graphically Enhanced Manuals")

http://DingDingMusic.com/Manuals/

'I may receive some form of compensation, financial or otherwise, from my recommendation or link.'

This is from memory... and also just a guess.

One of the updates contains a new and/or different way of identifying control surfaces, there are some problems that have plagued several users. What are you using as a Control Surface? The Logic update contains some new control surface definition files and some of them are wrong.

If you go to the Logic Pro menu item at the upper left of the screen, then to Preferences/Control Surfaces select "Bypass All Control Surfaces" does this change anything?