The phrase "a slight but persistent" is correct and usable in written English.
It can be used to describe something that is minor in degree but continues to exist or occur over time.
Example: "She felt a slight but persistent discomfort in her back after sitting for too long."
Alternatives: "a minor yet ongoing" or "a subtle but constant".
There were also pitch problems, mainly a slight but persistent sharpness.
As a consequence, the designs have felt reductive and static, with a slight but persistent look-at-me factor.
But the new polls also indicate a slight but persistent advantage for Obama in Ohio, the state whose electoral votes appear to be the most critical in determining which candidate will win the election.
The nitrogen content increased as the fermentation progressed, accompanied by a slight but persistent free N concentration increase.
In some cases, such patterns may be due to other adverse intrauterine conditions such as undernutrition 10 which may constitute a slight but persistent brain insult.
As patients with mild traumatic brain injury (mTBI) generally reveal no overt structural brain lesion on routine magnetic resonance imaging (MRI) or computed tomography (CT) scans, microstructural and neurochemical changes have been proposed to account for slight but persistent deficits in this population.
There is no recognized aetiology of these alterations; it is possible, however, that this slight, but persistent increase in chemokines and antibodies levels in the CSF of SLE patients elicits this damage by maintaining a chronic subclinical inflammation or progressive neuronal loss.
Participants had a slight but significant increase in cognitive function.
Thus, with the exception of a slight but significant effect in UVC-treated plants and plants exposed to 25 mM of NaCl, the transgenerational effect does not appear to be persistent in successive generations of untreated plants.
Similarly, nilotinib induced a slight but noticeable increase in Abl.
