getting error in transport saying unspecified error

Hello Experts,

I have an issue in creating transport in MDM,

We have two ECC system and we have in/out bound maintained for two ECC system but for temporary basis we need to stop interface to ECC2 so decided to change the processing type to manual from automatic in all in/out port for ECC2,

Below step followed,

Created transport reference (before doing the changes)

Selected export change file (delta) in console

We get option to select the changes to create delta file and I accepted all changes what is required,

After click OK button it takes some time after that I get error saying “unspecified error”,

Help to understand what the meaning of unspecified error and i have attched file for ref,,

Regards

Ajay