The only reason you imagine that there is a contradiction here is because you imagine that the scripures say He will only return one time. You fail to realize that the word "day" is OFTEN used in scripture as a generic term for a period of time whose length is undefined, as in "now is the day of salvation."
The scriptures could not be more clear in explicitly defining various periods of time associated with His return, ranging from "3 days," 30 days, (1290-1260) and 75 days, 1335-1260) through "add year to year," "year by year," and "in summer and winter" to "THE thousand years." (not just "A thousand years, but "THE thousand years."
So your claim that it all happens on a singe day is flatly contrary to a large number of explicitly stated scriptures. And that is the same with the conclusion that He will only return one time.
The scriptures clearly describe two separate gatherings that the Lord will make, in which He will gather two different groups of His own, to two different places, and at two different times. One of these gatherings is found in Matthew 25:1-10, John 14:2-3, 1 Corinthians 15:51-52, 1 Thessalonians 4:15-16 and Revelation 3:10. The other one is found in Isaiah 66:15-20, Jeremiah 16:14-16, Ezekiel 34:11-16 and Ezekiel 20:33-38, and Matthew 24:29-31.
How does any of that explain why those in the Luke 12 parable are shut out once the wedding commences, but then are blessed after the wedding has come and gone? If you are going to create a doctrine based on 2 parables, or that your doctrine has to do with these 2 parables, among other things, that means you need to be able to show how this doctrine reconciles these two parables, and not just claim these two parables prove Pretrib, and then not even bother to show how this doctrine reconciles these two parables.
Luke 12:36 And ye yourselves like unto men that wait for their lord, when he will return from the wedding; that when he cometh and knocketh, they may open unto him immediately.
37 Blessed are those servants, whom the lord when he cometh shall find watching: verily I say unto you, that he shall gird himself, and make them to sit down to meat, and will come forth and serve them.
38 And if he shall come in the second watch, or come in the third watch, and find them so, blessed are those servants.
39 And this know, that if the goodman of the house had known what hour the thief would come, he would have watched, and not have suffered his house to be broken through.
40 Be ye therefore ready also: for the Son of man cometh at an hour when ye think not.
Matthew 25:5 While the bridegroom tarried, they all slumbered and slept.
6 And at midnight there was a cry made, Behold, the bridegroom cometh; go ye out to meet him.
7 Then all those virgins arose, and trimmed their lamps.
8 And the foolish said unto the wise, Give us of your oil; for our lamps are gone out.
9 But the wise answered, saying, Not so; lest there be not enough for us and you: but go ye rather to them that sell, and buy for yourselves.
10 And while they went to buy, the bridegroom came; and they that were ready went in with him to the marriage: and the door was shut.
11 Afterward came also the other virgins, saying, Lord, Lord, open to us.
12 But he answered and said, Verily I say unto you, I know you not.
13 Watch therefore, for ye know neither the day nor the hour wherein the Son of man cometh.
Assuming your interpretation of these 2 parables, the following happens first----And while they went to buy, the bridegroom came; and they that were ready went in with him to the marriage: and the door was shut. Which then results in this---Afterward---saying, Lord, Lord, open to us---then the Lord saying, Verily I say unto you, I know you not. Watch therefore, for ye know neither the day nor the hour wherein the Son of man cometh.
This would obviously mean these meant in Luke 12:36-39, they initially did not watch, thus missed the wedding altogether, thus locked out of the wedding once the door has been shut. Even though they were locked out of the wedding, as were the 5 foolish virgins, the 5 foolish virgins are shut out of the kingdom forever, yet these in Luke 12:36-39 are somehow blessed all of a sudden, not before the wedding, but after the wedding, while these 5 foolish virgins remain unblessed after the wedding. IOW, assuming this scenario, they didn't get a 2nd chance like these in Luke 12:36-39 do. Why not?