苏二进制存在，但不能执行（从终端执行时没有错误，只需空） -- rooting 领域 和 root-access 领域 和 unrooting 领域 android 相关 的问题

My friend is having a little problem with his phone where he can't update or use banking software on it because of root even though he has never rooted it and root checkers gave me mixed results, some says its rooted and some says its not rooted. So after looking around i downloaded a terminal and ran "su", it ran without errors, but it didn't do anything and didn't output anything.

Now, im not fully sure if this is what is causing his phone to not be able to update, but it does seem odd to have the su file on the phone without it actually being rooted, my guess is that the phone was bought used and the previous owner was attempting to root the phone but failed and just gave up. So, now me and my friend are trying to find a way to get his phone "unrooted" even though its technically not rooted. What should we do?