Sticky oil painting, please help

Good day,
I have a problem with the drying of an oil painting and would like your scientific advice. The painting was built up as follows: absorbent gesso-acrylic primer on the canvas. Then it was finely sanded (to maintain a very fine texture), primed again, and sanded again. A total of 3 layers of gesso. Then it was painted with oil paint. Only turpentine substitute and drying poppy oil from Winsor & Newton were used for thinning. There were no problems so far. In certain areas, a fir varnish was applied, based on turpentine substitute or white spirits. This varnish has the same properties and is similarly composed as a damar resin varnish. This fir resin varnish was applied in several areas of the painting to achieve a specific effect. It was applied both thinned with turpentine substitute and undiluted. These areas dried quickly and became very hard. They were glossy, smooth, and rock hard. Overall, I let the painting dry for 1.5 years before I wanted to protect it with Gamvar varnish. Unfortunately, I didn’t get that far. Because I decided beforehand to oil out the entire painting with a very thin layer of the same drying poppy oil from Winsor & Newton, to preserve the underlying layers before applying the varnish so that they wouldn’t be accidentally removed by the Gamvar varnish. Unfortunately, this was a mistake on my part. The painting is still sticky after 8 months. It is noticeable that the oil is particularly sticky in the areas that were previously treated with the fir resin varnish. The relative humidity in the room is optimal and low, ranging from 48 to a maximum of 51 percent, and the room temperature, especially in the summer months, exceeds 25 degrees Celsius. There is UV light through the window. I have tried quite a lot to optimize the climatic conditions in the room, including purchasing a dehumidifier. Unfortunately, it has not been successful. I am at a loss as to what else could help. I do not dare to wash off the layer because the fir varnish underneath could be attacked by turpentine. Continuing to wait has not yielded any visible results. The areas still feel somewhat sticky. Can you please tell me what might be causing this sticky behavior? There are no plasticizers in the fir resin varnish (according to the components on the bottle) that could possibly be the cause. What else could I do? Should I simply varnish the painting with Gamvar varnish now? I am very grateful for any scientific and helpful response.Best regards,
Irina