In version 6, the mod works well in rendering with the mod Headcrumbs (spiral lucky block). But from version 7 onwards the skin gets buggy, the same happens with morph mod in multiplayer. Is there any way to fix it?

Can you describe how buggy it is in more detail? something like texture messed up.
A screenshot would be helpful too.
It's been a long time since i last worked on this mod.
From version 6 to version 7, it seems those changes does not have anything to do with actual rendering.

it is as if the skin did not look very well rendered, similar to version 1.6 when using the skin 64x64. But it only affects those mods. Headcrumbs 1.7.4
https://i.imgur.com/KYgVaGk.png

skinport v6 https://i.imgur.com/SbVkDBd.png

Does it also rendered weird in players? or is it only player heads?

The reason it renders weird is SkinPort doesn't have support for player heads to render a 64x64 skin.
If you are using Headcrumbs, you can try Et futurum, it is made by the same author.
Et futurum brings 1.8 features into 1.7, and it also has 64x64 skin support.
By digging through Headcrumbs' source code a little bit, i found out it has support for Et futurum.
If you just want 64x64 skin support and want player heads render normal, please tell me and wait a little bit for me to figure these things out for 1.7.

Only on the player heads. The player's rendering is normal.

Yes, it would be of great help. This mod corrects the multiplayer bug. But anyway, thank you.

I released 1.7.10-v9a, it added support for vanilla playerheads to display properly, and other features from recently updated OfflineSkins.
Unfortunately, only partial support for Headcrumbs has been implemented, and i didn't test with Morph.
You will need Java 8 to run this new version, Java 7 won't load.

Ok, thank you very much. I think it's because headcrumbs is set to the old skin pattern, or something like that. Because in other cases without headcrumbs or morph the skin works normally.