The power producing solar panels on the Sentinel-1A satellite have been damaged by an impact of some sort. The impacting object was tiny, in the few-millimetres class tiny. The image above from ESA shows the damage.
Even an impact with such a tiny object makes a difference:
A sudden small power reduction was observed in a solar array of Sentinel-1A, orbiting at 700 km altitude, at 17:07 GMT on 23 August. Slight changes in the orientation and the orbit of the satellite were also measured at the same time. — ESA
Sentinel 1A operations have not been impacted. There are in excess of 19,000 bits of known space debris, luckily this one was small.