intensity goal

Is it just me having this problem? Or does anyone use pace as a goal in structured workouts?

Not you only have this problem. Every short interval run (1-2 min long) counted so. Garmin counted pace as too big averaging not instance pace, i think it is 30 sec averaging base. Hence every time you start an interval you get "low pace" warning for a 1st half of a minute and you get a "too high pace" warning at the end of the minute.  See my 2 months old  post here. No one from Garmin is interested in this.

I have the exact same problem with the interval workouts. I had previously a Forerunner 245 that was working perfectly for the intervals and i changed for the Forerunner 955 expecting a much better watch but i am so mad because in one week, i will run the Boston marathon and i had so much difficulty to do my interval workouts because i was either too fast or too slow because my watch will give me the real accurate pace only after the end of the Lap. As you said piero you start the interval and the watch say, pace too slow ex: 3:50min/km and at the end of that lap, it show 3:40min/km even if the watch never show a pace faster that 3:45.  Perhaps the structural workout work fine if you do your interval between 7 and 8min/km pace but for a watch that supposed to be the best on the market, its a big letdown.  

i I open a ticket on Garmin customer service and after one week still no answer on that specific problem (i have also display issues that was answered)

Please Garmin, adress that issue that plagued my watch since my purchase last September ️

I wrote several times to Garmin to explain the problem but the only answer is a hard Reset, which obviously doesn't solve anything 

This is an ongoing issue - it's a huge fail by Garmin that makes the workout screen unusable for speed work, or for any performance targeted training actually.  Apart from the fact that the "actual" pace shown is only given to the nearest 5 seconds it swings either way by up to 15 seconds seemingly at random.   It's impossible to reliably achieve your target average pace - we have to create another data screen for that, so what's the point of the workout screen? 

Runners have been using average pace since they invented clocks - can we have that on the workout screen please Garmin?  Just change pace to lap pace and we'll all be happy.   

from my experience, what helps a bit is setting the range not to 5, but to 10 sec - i.ex. 3:40-3:50. Plus, length of the interval must be long enough, so that the watch will have time to 'handle' everything.
 
I stopped using structured workout for intervals like 100 or 200 m cause it doesn't make sense - you never get reliable data on the screen. If you go from 500m up, then it makes more useful. Short distances I run based on my feeling - thanks to this super advanced 955 model :) The same store was with 945 or F6 series. 

Generally it's a shame for Garmin, despite all the new sensors and GPS chips, they're still not able to handle short time avg pacing. Go to any other brand, and they have no problems with this!

My feeling is, that Garmin simply doesn't care about such points, as their main customers can be found in other groups, not the one doing such workouts ;)

The 945 provides 200m lap pace with no problems, just takes a few seconds to stabilise.   For some reason they use the incorrect field on the 955 - lap pace is always being computed and as far as I can tell it's completely ok, just not shown on the workout screen.  A really weird decision for sometihng that's supposed to be a premium running watch.

I end up having to set 30 secs above and below target pace just to stop it constantly giving alerts, 15 seconds isn't always enough.  

My ranges are always above 1000m. with pace target in a range of 10 seconds. The problem despite my pace being constant is always present and therefore I avoid using the goal of the pace. With the 645 that I had before, the problem wasn't there. 

so to sum up - with the top model of Forerunner series now (next to 965), we are not able to receive even close to accurate short time pace on the screen :)

I know, that in the interval summary it will present proper value, luckily I can justify myself more less what is the current pace.  BUT - let's face it, this function is not working. You buy an expensive gadget to help you with training and it does not, as it gives wrong current reading during the training phase. From many years it is a problem in Garmin watches - just look after the training at tempo graph in Connect - it bumps up & down constantly.

Setting a +/- 30 sec. tempo range may be an answer from watch alerts, but it makes no sense in training. If I want to run 4:00 / km, I set 3:55 - 4:05, not 3:30 - 4:30 which is way too wide. In such scenario you have to take a watch too frequently as the watch itself doesn't guide you at all. You can run 4:15 or 3:50 an it will be 'still fine'. Nonsense.