I have noticed that Vector Tiles do not behave as expected in Google Chrome. I have the most up to date version of Chrome. Tiles will appear blocky or expand past their boundaries causing polygon colors to overlap portions of a map. This occurs in the Sample Code sections of both 3.16 and 4.0 APIs. I do not see this same issue in Edge, FireFox and IE.
Is this a known issue with Chrome? It appears to behave in Chrome on iOS.
Based on your screenshot, it looks more like a (common) hardware issue. Though it is a bit strange if it differ between browsers (I assume you tested on the same machine).
"Vector tile layers have the best performance on machines with newer hardware."
VectorTileLayer | API Reference | ArcGIS API for JavaScript 4.0
Is your PC several years old? On an older PC in a meeting room my Vector Tiles were completely wacked with parallel stripes. So I remote accessed my newer PC and they then looked fine.
I have seen a somewhat similar problem while testing vector tiles. The tiles disappear at certain zoom levels - see attached zoning map image where there are large blank gaps. Vector tiles published via Pro 1.3.1.
In our case, the problem is evident on 3 browsers (Chrome, Firefox and IE 11) and on different PCs. Our PCs are anywhere from 2-4 years old (Win7, Dell, Intel Xeon 3.6GHz, 16GB RAM). I have not determined if it is a data problem, but at other zoom levels the tiles display fine.