My 15 week old puppy has developed a chewy grip on the jute puppy sleeve. At 10 weeks old he would grip very well. How can I resolve this?

First of all, I would stop tug and rag work for right now as many pups actually start the teething process around 14 weeks and may be mildly uncomfortable which can cause a change in grip. I don't believe you will hurt anything by just putting biting games on hold for now.

You may be using an item that isn't as enjoyable for him, I don't use puppy sleeves or leather with most young pre-teething puppies even if I know they can probably bite it. I use soft toys that they really can dig into and enjoy. Early bitework is more about creating desire for the activity than working on grip like you would with an older dog. You won't hurt anything by using soft toys. I used the toy I linked below here with my current puppy (a GSD) . He was able to bite a jute puppy sleeve, he actually had an amazing grip from 8 weeks on but since my early training is more about the activity being fun than working grip with young pups, I used the toy he absolutely loved to hold onto. Once he was completely done teething at around 6 months I moved on to soft puppy sleeves. A leather rag has its place in training but it can be demotivating for some puppies because it's hard to hold onto. You want to make lots of success, not lots of challenge right now.

Of course we want to reinforce a good grip but I don’t make it difficult for small puppies, I build them up by making it fun and easy for them and if I see a change pre-teething I will usually just put grip work on the shelf until the adult teeth are in and reevaluate at that time. I hope this makes sense.