《经济学人》中的难题句的语法剖析

经济学人里的句子，请问第二句话的语法是否有问题？

But in 2012 the KNU signed a truce with the army.

It laterjoinedthe peace process, progress on which has been touted by Aung San Suu Kyi as her priority since she became Myanmar’s de facto leader in 2015.

It laterjoinedthe peace process, progress on which has been touted by Aung San Suu Kyi as her priority since she became Myanmar’s de facto leader in 2015.

逗号后为非限制性定语从句修饰the peace process。关系代词which指代the peace process, 在从句中做介词on的宾语，介词短语作从句主语的定语。