Are you not sure how much your oven heats up exactly? You will not be able to control the results.
If the eclair cracks, the temperature is too high and it must be reduced.
Usually I recommend decreasing by 10C (50F) and monitoring the result.
It's all about the eggs
The amount of milk and water in the recipe are constant, but it's not the same when it comes to the eggs.
If the recipe says 220 g (7.80 oz) of eggs, today you may need 180 g (6.35 oz), and tomorrow even 240 g (8.50 oz).
It's OK. In making cream puff pastry, we focus on the consistency of the dough.
Air bubbles that got into the eclair when kneading the dough or putting it into a bag.
When heated, they expand and go out through the body of the eclair; the cracks are short and placed at random.
In the video I show one of the ways to get rid of air bubbles.
Strong heat from below
It results in long cracks closer to the bottom of the eclair.
The temperature in the oven may be adequate, but when you use a silicone mat, for example, which conducts the temperature well, the cracking of the eclair can take place.
Just think about it, and may the perfect eclairs come with you!
I will be pleased to hear if this information is useful!