I earnestly ask: why does the activity of platinum carbon drop significantly after being soaked in methanol for half an hour?

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The solvent for the platinum-carbon catalyzed hydrogenation reaction is methanol. A strange phenomenon has been observed recently: when the catalyst is soaked in methanol, its activity drops significantly, to the point where the reaction results become unsatisfactory (substrate content ≥2%). Since the contact time between the catalyst and the solvent directly affects the catalyst’s activity, it is necessary to shorten the operation time for all steps prior to the hydrogenation reaction. First experiment: In a pilot scale test, platinum carbon (unused) was soaked in methanol directly for 0.5 hours (without any additional procedures); a reaction occurred between methanol and the platinum carbon, resulting in plates that did not meet the quality standards. Wash with water to displace methanol, filter under vacuum to dry it, and the resulting dried filter cake (platinum carbon) is tested for reaction suitability (substrate level ≤2%). Second experiment: After soaking platinum carbon in a certain amount of methanol, the platinum carbon was filtered out, and both the platinum carbon and the methanol in the filtrate were subjected to catalytic hydrogenation reactions (all other additives remained unchanged). It was found that the reaction rates in both groups were poor. From the above experiments, we analyze that some reaction must occur between methanol and platinum carbon; the products of this reaction have a significant impact on the catalyst’s activity. These products can be washed away by water, and the fact that reactions are less effective when using methanol that has been soaked in water indicates that these products are soluble in both water and methanol. I really want to figure out now what reaction takes place between methanol and platinum carbon, and what are the products? I would appreciate some guidance from the experts