It's very common. My car still does it a bit from cold after a gearbox rebuild, though I'm not sure the synchro's were replaced, possibly swapped over as I had a working box built from 2 boxes plus a box of gears and cogs after I toasted mine through oil starvation due to a broken cooler pipe. I'm using Swepco which is very thick, but I find after about 5 mins there is no issue. If I let it idle for a minute or two before I set off the problem lessens. Of course, changing the oil can only help, 75/90 I think is standard, the Swepco is 80/90 which is likely to make the issue worse, however I find Swepco makes the box quieter in general, has a super long service interval, and is well thought off in the transaxle world. You will find others disagree!
You will probably find 3rd to 2nd is fine, and when going from 1st to 2nd on a cold box, if you let the gear selector centre on your shift, you won't have a problem, eg, out of first into neutral, then into 2nd. I certainly do anyway and it is my work around. Personally I would change the oil and see how it is, then choose if you can live with it or not, get a 75/90 synthetic oil. I think a S2 box needs about 2 litres if it doesn't have a cooler. I'm quite happy to shift via neutral for a mile or so till it settles down. Your car, your call!
Stuart