You have unlocked the ability to do it, you have gained permission. You still have to build up the cumulative modifications for any module.Not being a rabid engineering pilot, I don't recall this before.
I wanted to engineer 3 of my 0A shield boosters (all 3 the same type). I brought the first one up to lvl4, then switched to the 2nd of 3 boosters, and had to start over unlocking them again at lvl1 blueprint as lvl2 and above were locked again! Is this normal behaviour?
I would think that if I've unlocked to lvl 4 on "a" shield booster .. it'd be ALL shield boosters .. not just that one specific one.
Usually grade one is one or two of an easily obtainable mat you can store a lot of, grade two mats are slightly more complex and require slightly more, all the way up to G5 where it takes quite a few fairly rare mats quite a few goes. If you pin the recipe you can apply the special at grade 1 then do the rest at any station with a workshop once your mats bins have enough to progress more.
So yes, it is normal behaviour