First work out the cause. Fairly obviously it is due to the thread not being pulled up as the needle retracts. But why? There are several causes, and several possible solutions. One cause is too much drag on the thread, but another cause is a misbehaving presser foot on the machine. That said, changing the bottom tension is not needed or wise. Leave it alone.
Thread drag cures include:
Very large needle: may or may not work. More of a solution for breaking fine needles on tough fabric.
Polished thread. Many cotton and cotton blend threads have a high surface friction, while pure syhthetic threads slide a lot more easily through the fabric. However, pure polyester threads can be a bit tricky to handle as they can kink. Bonded nylon thread is good stuff for heavy fabrics. A good poly-cotton is a good GP thread.
'Leather' or triangular needle. This actually cuts a larger hole so the thread pulls up easily. Disadvantage: the cut hole. Works fine on leather where the cut hole does not matter too much, but may damage fabric threads.
Lubricate the needle and thread. This may be needed if it is the coating which is dragging. This can happen if you sew very fast, soften the coating and gum up the needle. It also happens everytime you try to sew through wet silicone or PU adhesive! Disadvantage: oil on the sewing. I have yet to try water to cool and lubricate the needle and thread. (Commercial machines sometimes have oilers attached near the needle.)
Talc powder or fine chalk may also help prevent stiction from coatings or very tight fabrics - sometimes. I don't have a lot of hope though.
If the presser foot lifts as the needle retracts you will get loops. The reason is complex. The lifting of the foot is sometimes due to the spring on the presser foot being weak or set too soft to resist the needle drag. That much is obvious.
Why the loops happen is due to the mechanism inside the machine. When you deliberately lift the presser foot you release the tension on the top thread (levers etc are involved) so you can drag the thread and the fabric away. OK, but if the foot lifts through drag on the needle, this upwards movement of the presser foot can also briefly release the tension on the top thread, right when it is most needed. This problem is not all that well known.
If you can adjust the presser foot spring, try tightening it. However, be aware that a high presser foot force can damage light fabrics like silk, silnylon etc.
If you are sewing a short distance or slowly, press down on the presser foot with your finger as the needle lifts. Try not to sew through your finger: the blood marks the fabric and you may break the needle.
If you are sewing for a very short distance (eg applying webbing), turn the machine by hand and rock the needle back and forwards before lifting the needle for each stitch. This may ease the hole and let the needle extract, but it is rather slow.