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There are two issues.
1, PLA have very high friction on bare metal. The hole for filament is not exactly 1.75mm but rather around 2mm. When it get warmer and is under pressure (as it do above heatblock on the bottom of cooler) it will expand, stick to the inner sides of the metal throat, and stuck there. This will not show unless you try to print. When you extrude filament into free air, you usually extrude quickly, so the fillament don't have time to expand. Troubles starts when you print slowly.
2, The Chines clones of E3D v5 have a gap above throat in the aluminum cooler. You can check it by caliper. The threaded part of throat that is inside of the cooler is typicaly 20mm, but when you measure the hole for throat, it is around 23-24mm. Throat won't go deeper because the thread is not made all the way down (it is not fault of Chinese, it can't be technicaly done). For this reason E3D v6 have a teflon tube 4/2mm (OD/ID) going through cooler to the upper part of throat. And for the very same reason throat of v6 have M7 thread filled flat on the top.
To prevent filament jamming try to use throat with teflon tube inside and if it is possible drill bigger hole in cooler too, so this teflon tube can go through the whole aluminium cooler and throat in one piece and guide filament all the way down to the nozzle.