Musleh al Umma Maulana Shah Wasiullah Allahabadi (Allah have mercy on him) said,

‘As it is possible that an individual has knowledge and he does not practice accordingly, similarly it is possible that one practices (according to the knowledge) but without sincerity (ikhlaas).  

Moreover, it is possible that previously there was sincerity in actions done but later it evaporates. 

Shaykh Muhiyuddeen Ibn Arabi (Allah have mercy on him) said,

وقد راینا شیوخا” سقطوا

We saw many Shuyukh that fell from their ranks (as a spiritual guide due to this). 

If even a Shaykh can fall (from his rank), then possibility for a mureed to fall (due to lack of sincerity) is much greater.’

Majales Musleh al Ummat ra, volume 6, page 134