The problem may be due to poor workmanship.

问题可能是出在拙劣的工艺上。

《柯林斯英汉双解大词典》

It's evident that the rust is due to poor workmanship.

事实表明生锈是因为粗糙的工艺。

youdao

As well as saving time, this process limits the risk of defects resulting from poor workmanship on site and also significantly reduces the disruption from operations on site.

这个过程不但节约时间，而且降低了现场工程质量低劣造成的缺陷，也显著降低了现场作业会突发的中断事故。

youdao

The workmanship was poor.

VOA: special.2009.02.22

Jane: If there is evidence of poor or dangerous workmanship Corgi do act.

BBC: Frontline Scotland graphic