When uploading a "Classic" skin with the narrow/Alex type arms (with 3 pixels) everything is peachy keen. However, when you exit the game, upon reopening your "Classic" skin is automatically converted to a wide/Steve type arm, which causes weird graphical errors such as erroneous black or transparent lines. This is really frustrating as the only workaround is to manually re-upload the classic skin every single time you open the game.
This only affects classic skins. Skins made in the native skin editor carry over the arm size appropriately.
A recent thread on Reddit that explains the same issue:
https://www.reddit.com/r/Minecraft/comments/1ger91w/how_come_my_mc_skin_keeps_doing_that/
See screenshots. First screenshot named "NarrowNormal.png" shows what it looks like after uploading a Classic skin and selecting the narrow arms. The second screenshot named "AfterReopen.png" shows what the skin looks like after closing and reopening the game. Notice that the arms are 4 pixels wide, but the 4th row is completely transparent.
Linked issues
duplicates
Attachments
Comments

Thank you for your report!
We're tracking this issue in MCPE-186591, so this ticket is being resolved and linked as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support (Technical Issues) – 📧 Microsoft Support (Account Issues)
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki
-- I am a bot. This action was performed automatically! The ticket was resolved by one of our moderators, and I left this message to give more information to you.