What are the most common problems in Lenovo phones?

Mostly , people didn't like the ROM . It did not have app drawer plus was not much close to stock rom with too much visual costumiztions.

But they have changed that in new phones (Vibe X3) , brought in the app drawer and a mode that helps it look closer to stock.

But still it has few bloat ware apps , plus Camera on lenovo phones suffers a lot . Sometimes the post processing is overly done and images loose a lot of detail .

Plus comparatively the touch and display on motorola phones seem better .

But as you know they have acquired motorola they would be improving with future phones.

n our (25 person) complex there are a few iPhones (mine an iPhone 6) an awful lot of Lenovos and only a few Samsungs (low cost versions which once dominated the scene). 
In a formal in-house survey on My Phone Complaints covering all phones: the Samsungs were in first place (most complaints) then the Lenovas and the least problematic by far - the iPhones.

Ranking top 3 Lenovo problems. 

• 1 - Mushy home button on pressing and sometimes no response. In some cases it is the MS program hogging the I/O not just a mechanical issue.
• 2 - Crash or Hang or sometimes Hang or Crash. Obvious that the respondents wanted to say it just stopped working. Hangers were 75% to the crashers 25%. Again it can also be attributed to program compatibility problem. Whatever the cause of reason for this it was so frustrating to Lenovo users.
• 3 - Battery. Two issues: a) fully charged phone after start using it there is a big drop  (15-25%) within minutes. The next day fully charge the phone and battery runs normal. b)  Battery working fine but in the status level of  50-60% it plummets down to 3-7%  it's not a rare occurance nor happens every day but according to the group it happens and yet not to frequently

And if you think Lenovo has problems which it does it has far, far less than the lower costing Samsung's.