The Seventh-day Adventist denomination grew out of the failure of the prediction of William Miller that Christ would return in the Second Advent during an 1843 to 1844 time period. It formally organized in 1863. Those early leaders came from a variety of religious backgrounds. While Ellen White came from a Methodist background, James White and several others came from what has been called the Christian Connection. Other early leaders came from other denominations.
The Christian Connection rejected the Trinitarian position on God that is generally held by Christians today. It took what is called a Deist position on the Trinity. Other early leaders in what became the SDA denomination, even if not associated with the Christian Connection took positions on the Trinity that were not in accord with the Trinitarian position held today by most Christians. NOTE: Joseph Bates James White and Uriah Smith were all associated with the Christian Connection.
It is well known the Ellen White, in the early days of this denomination did not hold to a traditional position on the Trinity. However, as with other doctrinal beliefs of Ellen White, her beliefs on the nature of God changed over time and she moved to a more traditional position on the Trinity.
In truth, many early references by our early leaders show that they had a confused understanding to the Trinity doctrine that they rejected. Some of the heretical views on God included Docetism, Modalism and Tritheism. Some have described the early Adventist as Semi-Arian.
J. B. Frisbie’s view on the Trinity is not totally clear. But it is possible that he may have accepted Docetism. In any case, his understanding of the nature of God was seriously flawed. NOTE: Docetism taught that Christ was a spirit with no real body.
Joseph Bates totally misunderstood the Trinity Doctrine. He thought it taught that Christ and God the Father were one and the same being, which is false. He strongly condemned Modalistic Monarchianism. From this perspective, he rejected the doctrine of the Trinity. NOTE: Modalism teaches that the one God appeared in three different versions (forms).
John Loughborough rejected the Trinity because he believed that it taught Tritheism, which involves the existence of three Gods.
J. M. Stephenson, a one-time SDA preacher, taught that Christ was a created being.
In a historical understanding of the development of Christian doctrine, it is clear that early Christian leaders developed their doctrinal understandings over a period of time. They did not come into immediate perfection in understanding. Justin Martyr, writing in the Apology made a major contribution in his identification of Christ as the cosmic Logos. However, some of his statements come close to Tritheism.
NOTE: The above, which I have written, has been based upon the following book
Paul Peterson & Rob McIver, editors. Biblical and Theological Studies on the Trinity. Avondale Academic Press, 2014, 251 pages.
I have not researched the theological beliefs of W. W. Prescott (1855-1944) regarding the Trinity. The following website may be of interest in this respect, and I am going to have to give it further consideration.
https://www.asitreads.com/w-w-prescott
NOTE: I just came upon this and right now I am short on time and I do not have the time to give extensive thought to what I read on that website.
I do hold consider any SDA leader to have the total of all truth. All of us humans need further development is some aspects of our doctrinal beliefs. If Prescott was wrong in his understanding of the Trinity, that does not mean that he was wrong on everything else that he believed.